Propeller Induced Complete Transformation of the Secondary Structure of a Dipeptide on Water Surface Controlled by Chiral Supramolecular Assembly

doi:10.21203/rs.3.rs-3771832/v1

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Propeller Induced Complete Transformation of the Secondary Structure of a Dipeptide on Water Surface Controlled by Chiral Supramolecular Assembly

https://doi.org/10.21203/rs.3.rs-3771832/v1

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Water surface provides a unique platform for the directed formation of self-assembly and transformation of secondary structures of peptides and proteins. Here we report a well-defined supramolecular assembly controlled complete one-step transformation of the secondary structure from β-sheet to α-helix of an amyloid-derived dipeptide system on the water surface. Spherical aggregates and molecular wires containing β-sheet structure are converted into two-dimensional (2D) molecular sheets comprising large planar area yet with a molecular level thickness with α-helix structure. The conformational features of the β-sheet to α-helix structure transformation are dominated by the abundant intermolecular hydrogen bonding, π–π stacking and C–H···π interactions. Strikingly, the dynamic change in the dihedral angle between the aromatic rings of dipeptide at the water surface alters the molecular packing and shortens intermolecular hydrogen bonds with larger binding energies required for the secondary structure transformation. The novel one-step strategy reported herein offers an exciting example of the supramolecular assembly controlled secondary structural transformation of the dipeptide on water surface.

Physical sciences/Chemistry/Supramolecular chemistry/Self-assembly

Physical sciences/Materials science/Soft materials/Self-assembly

The self-assemblies of peptides and the intramolecular interactions in proteins leading specific folding motifs have attracted a considerable attention across the fields of structural biology, medicine, chemistry, physics, and materials science.^{1, 2} Secondary structures such as β-sheets and helices (e.g. α-helix and supramolecular helix) are the major structural motifs that facilitate the organization of the three-dimensional conformation of proteins.³ Both α-helix to β-sheet and random coil to β-sheet transitions could occur during aberrant protein folding and assembly.^{4, 5}The formation of β-sheet in amyloid fibrils is believed to be related to the consequences of some amyloid-associated diseases.^{5, 6, 7} Thus, the structural transformation of the stable and highly ordered β-sheet into the α-helix bears important implications for inhibiting amyloid fibril formation and still remains an urgent unmet challenge.^{8, 9} Many attempts have been made to explore the transformation from β-sheet to α-helix structure using peptide building blocks.¹⁰ External stimuli have been utilized to initiate and control the structural transformation of model amyloid assembly, including temperature,^{11, 12, 13, 14} pH,^{15, 16, 17}metal ions,^{15, 18, 19} chemical reactions,²⁰ ion strength,²¹ X–N Acyl migration,²⁰ co-assembled additives^{22, 23} and charge-induced strategy.²⁴ However, establishing a simple one-step yet comprehensive route towards the transformation of the secondary structure based on the dynamic molecular conformation change still remains a pressing need.

Building blocks comprising dipeptide of L-phenylalanine (FF) afforded original insights into the formation of specific secondary structure.^{12, 25, 26} FF forms the central recognition motif of the self-assembled structures through strong aromatic–aromatic and hydrogen bonding interactions.^{25, 27, 28} These local interactions dictate long-range structural order and particular secondary structure formation. Therefore, it is important to explore intra- and inter-molecular interactions based on the conformational dependency underlying FF-based assembled supramolecular structures. In this regard, supramolecular assembly on the water surface is highly relevant allowing a high degree of conformational control and intermolecular interactions to achieve secondary structure transformation. Although there are numerous conformations accessible to FF in water, the supramolecular assemblies on the flat-water surface permitting the secondary structure transformations are rarely observed. Herein, for the first time we report a one-step approach for the complete transformation of secondary structure from β-sheet to α-helix structure of a tetraphenylethylene-FF (TPE-FF) derivative on the water surface. We found that the dynamic change in the dihedral angle (ǀθǀ) between the aromatic side chains of FF with the aid of the surface pressure is a key parameter for altered aromatic and hydrogen bonding interactions leading to the complete transformation of the secondary structure. In particular, spherical aggregates and molecular wires (SMWs) with β-sheet conformation are formed at a higher ǀθǀ of 157º. Two-dimensional (2D) molecular sheets with large planar area yet with a molecular level thickness of α-helix structure are formed by the merger of SMWs at a lower ǀθǀ of 111º. Crystal-like conformation became the dominant form in the SMWs and 2D molecular sheets, permitting a highly ordered supramolecular packing of TPE-FF that is energetically favorable. The decrease of ǀθǀ alters the binding energies due to shorter intermolecular hydrogen bonds reinforcing stacking of TPE-FF into 2D sheets via H-bonding and C–H···π interactions. The complete transformation of the β-sheet to α-helix structures are evidenced from the atomic force microscopy (AFM), grazing-incidence X-ray diffraction (GIXD), circular dichroism (CD) and Fourier transform infrared (FTIR) measurements. The proposed β-sheet to α-helix transformation is further reinforced by density functional theory (DFT) calculations.²⁹ These findings provide a novel one-step approach for the complete secondary transformation by controlling the conformation FF-based derivatives in the supramolecular assemblies by employing Langmuir-Blodgett technique on the air-water interface, leading to the ability to tune peptide properties, such as piezoelectricity and Circularly Polarized Luminescence (CPL). These tunable properties make them advantageous for utilization in nanotechnology.^{1, 12, 30, 31, 32, 33, 34}

Herein, we report the results of the investigation of the hitherto unprecedented self-assembly structure formation by a system comprising of the Phe^L-Phe^L dipeptide core attached with an AIEgen luminophore known as tetraphenylethylene (TPE) to the C-terminal of this dipeptide, previously found to be key to the nucleation and self-assembly of peptide regions into functional structures. The FF dipeptide alone has been reported to form discrete and well-ordered tubular nanostructures.²⁷ The FF based nanotubes thus formed share certain structural features with the amyloid fibrils as they have similar vibrational spectral properties as compared to those of fibrils.³⁵ Owing to the fact that the TPE moiety adopts a propeller-like conformation with one double-bond core stator (stationary part) and four phenyl rotors (movable parts), we have covalently conjugated the TPE moiety with the amyloid-forming dipeptide, FF via amide coupling with the N-terminal amine of the former (TPE-FF). In non-polar solvents, the rotors may rotate easily against the stator via the single-bond axes, while in polar solvents, the intramolecular rotation may be restricted due to the physical constraints. The route to the synthesis of the amphiphilic TPE-FF (1) (Scheme S1) are given in the supporting information (SI).^{12, 15, 16, 36, 37} TPE-FF was extensively characterized using diverse spectral methods e.g., FT-IR, ¹H-NMR, ¹³C-NMR, ESI-MS etc. (Figure S2-S5) and the spectral data obtained were consistent with the assigned molecular structure. In order to delineate the role of the TPE end-group in the self-assembly of the dipeptide, we also synthesized a control dipeptide Perylene-FF (2), where the TPE group was replaced by a rigid, planar perylene moiety. Furthermore, another control dipeptide was synthesized wherein the FF was substituted by the dipeptide L-alanine (AA) to yield TPE-AA (3). The details of the synthesis of 2 and 3 are given in Figure S6-S8 and Figure S9-S11 respectively.

While the bulk properties of FF and related peptides have been examined extensively, not much is known about their behavior at the water surface. It is of interest to further examine the changes in structure when the molecules are compressed into aggregation by external stimuli like pressure. The presence of hydrophobic TPE and hydrophilic NH₂-FF groups made TPE-FF amphiphilic. This allowed the formation of a stable monolayer on the water surface upon spontaneous spreading from a chloroform solution. The surface pressure (π) versus area per molecule (Å²) isotherm showed a liquid expanded region at low surface pressure which was followed by the manifestation of a liquid condensed region till π = 16 mN m^− 1 (Fig. 1, red curve). A long plateau appeared beyond π = 16 mN m^− 1 indicating a pronounced conformational change of TPE-FF at the water surface upon application of pressure. Atomic force microscopy (AFM) images of the monolayer deposited at surface pressures below the plateau region revealed the formation of uniform thumb-shape domes spanning over several square micron areas (Fig. 2a-c). Higher resolution AFM images revealed that the domes consist of uniform spherical aggregates (Fig. 2e). Cross-sectional analysis of the AFM images showed a uniform height of ~ 4.5 ± 0.5 nm and a diameter of ~ 75 ± 10 nm for the spherical aggregates (Figure S12). Interestingly, few molecular wires of several microns length that appeared within the domes and spherical aggregates at π = 10 mN.m^− 1 (Fig. 2b and 2f). The population of molecular wires increased at a higher surface pressure of 15 mN.m^− 1 (Fig. 2c and 2g), indicating that TPE-FF possesses a substantial propensity to self-assemble into nanostructures of higher aspect ratio. Cross-sectional analysis of the AFM images revealed a height of 4.5 ± 0.5 nm and diameter of 75 ± 10 nm of the molecular wires, which were of the same dimensions as that of the spherical aggregates (Figure S13 and S14). These observations suggest that the molecular wires were presumably formed via the merger of the spherical aggregates. Interestingly, a drastic change in the morphology of TPE-FF assembly was observed beyond the plateau region. AFM images revealed formation of 2D molecular sheets with large planar area at π = 20 mN.m^− 1 (Fig. 2d). The planar area of the uniform 2D molecular sheets exceeded over several square microns, however, the thickness (4.5 ± 0.5 nm) remained the same as the spherical aggregates and molecular wires (SMWs) (Fig. 2h and S15). The morphological analyses clearly revealed a transition from the spherical aggregates to the 2D sheets via the formation of molecular wires upon a single step compression at the water surface. Various interesting morphologies of peptides including nanotubes,²⁸ microtubes,³⁸ microrods,³⁴ microvesicles,³⁹ nanofibers,⁴⁰ plate-like crystals,⁴¹ nano-donuts,⁴² cylindrical micelles⁴³ and nanotapes¹ were reported earlier. However, the formation of 2D molecular sheets with few molecular length thicknesses yet with large planar area by the merger of spherical aggregates at the water surface is hitherto not reported and is a unique manifestation of the supramolecular assembly of the TPE-FF.

The self-assembled morphologies and the conformational transition of TPE-FF at the water surface appears to be closely associated with the inter-aromatic interactions among the phenyl rings of TPE and phenyl side-chains of FF. The change in the dihedral angle (ǀθǀ) between the phenyl rings of FF during the monolayer compression on the water surface holds the key to promote the inter-aromatic attractions. Xiong et al. reported various self-assemblies of FF using a hybrid-resolution simulation model termed as PACE.⁴⁴ The resultant conformation of FF was found to depend on the position of the side-chains around the peptide backbone depending on the ǀθǀ. Hollow tubes of FF were formed for lower ǀθǀ < 60° while spherical or rod-like assemblies were obtained for higher ǀθǀ > 115°. In order to examine these traits in the present self-assemblies, we investigated the energetics of TPE-FF as a function of the ǀθǀ using DFT calculations (Fig. 3a). The constrained potential energy calculations were carried out at different ǀθǀ values in order to obtain the energy minimized conformation of TPE-FF. The potential energy versus ǀθǀ plot showed two minima at ǀθǀ = 111º and ǀθǀ = 157º respectively corresponding to the two stable conformations of TPE-FF (Fig. 3b and 3c).

On the basis of the DFT calculations of TPE-FF and upon comparison with the theoretical study of FF by PACE, we propose herein that TPE-FF exhibits change in the ǀθǀ between two phenyl rings of FF moiety during the compression on the water surface. The water surface acts as a template for the TPE-FF where the phenyl rings of FF and TPE moieties interact in a different way based on the change in the ǀθǀ of FF moiety. At a lower compression, the phenyl rings of TPE-FF remain apart on the water surface to mitigate the hydrophobic-hydrophilic repulsion. At this stage, the phenyl rings of FF moiety create a large ǀθǀ of 157º owing to the relaxed conformation of TPE-FF (Figs. 1 and 3b). Concomitantly, AFM morphologies reveal the formation of SMWs at lower compression (Fig. 1 and Fig. 2e-2g). These morphologies are similar to the simulated morphologies of FF by PACE, which shows formation of spherical or rod-like aggregates for large ǀθǀ.⁴⁴ Further enhancement of the compression changes the ǀθǀ between the side-chains of FF moiety to a lower value of 111º to facilitate the interactions among the flexible phenyl rings of FF and TPE moieties (Figs. 1 and 3c). The intra- and inter-aromatic interactions among the phenyl rings of the neighboring TPE-FF in the close packed configuration at the higher compression transform the SMW into 2D molecular sheets (Fig. 2d and 2h). Apart from the aromatic π···π interactions, other stabilizing forces including the hydrogen bonding, and the interaction with the water molecules and the FF backbone are to be accounted for the assembled morphologies of TPE-FF as observed earlier for peptide assemblies.^{45, 46} In fact, such interactions are evident from the DFT calculations carried out for the dimeric and tetrameric assemblies of TPE-FF with smaller ǀθǀ of 111º and larger ǀθǀ of 157º, respectively (Figure S16). In comparison to these self- assemblies on the water surface, a marked morphological difference was evidenced in the drop-casted assemblies of the soluble TPE-FF. At lower concentration, the drop-casting of TPE-FF solution formed ring shaped assemblies (Fig. 3d). The drop-casting of TPE-FF solution at higher concentration showed the presence of porous assemblies consisting of rings (Figure S17). Interestingly, these porous assemblies are in parallel agreement to the morphologies of FF assemblies obtained at ǀθǀ = 90° in the PACE simulation.⁴⁴ These diverse morphologies imply that TPE-FF molecules undergo conformational changes when exposed to different surroundings. However, transition of SMWs into large area 2D molecular sheets on the water surface with the aid of compression establishes a truly novel approach for controlling the orientation and packing of TPE-FF supramolecular assemblies for the secondary structural transformation.

To elucidate the internal structures of the TPE-FF assemblies, grazing incidence X-ray diffraction (GIXD) measurements were made for the SMWs and 2D molecular sheets (Fig. 3e). Diffraction peaks observed both for the SMWs and 2D molecular sheets indicate manifestation of strong interactions among TPE-FF that led to the formation of crystals on the water surface. The GIXD peaks appeared at 2θ = 1.16° (d = 7.54 nm), 2.05° (d = 4.30 nm), 9.4° (d = 0.94 nm) and 20.80° (d = 0.44 nm) respectively for the SMW. GIXD pattern showed similar peaks for the 2D molecular sheets except for the appearance of a small angle peak at 2θ = 1.95° (d = 4.52 nm) and reduction of 2θ = 2.05° peak intensity. The d-spacing of 4.30 nm corresponds to the thickness and corroborates with the thickness obtained from AFM height profile analyses of the SMW and 2D molecular sheets (Figure S12-S15). The d-spacing of 0.44 nm may be assigned to the π−π stacking interactions among the phenyl rings and multiple scattering from aromatic stacking of TPE-FF.^47,48 Molecular packing within the supramolecular assemblies is further elucidated based on the correlations of GIXD measurements and DFT calculations (Fig. 3f). DFT studies revealed an antiparallel arrangement of TPE-FF dimer, where TPE units are located in opposite directions to establish effective intermolecular hydrogen bonding interactions through the -NH₂ and -CONH groups (Figure S16a and d, Table S1). The TPE-FF dimers aggregated in the tetrameric assembly with binding energies of 45 kcal and 33 kcal for ǀθǀ = 111º and 157° respectively (Figure S16c, f). Manifestation of a number of C–H···π interactions were also evidenced imparting additional stability to the tetrameric assembly. The difference in binding energies originated from the strengths of intermolecular hydrogen bonds at different ǀθǀ. Accordingly, the hydrogen bonds are shorter (1.95–1.98 Å) for lower ǀθǀ = 111º in comparison to the ~ 2.0–2.1 Å for higher ǀθǀ = 157° (Figure S16a, d). The decrease of ǀθǀ to 111° changes the binding energies due to greater intermolecular hydrogen bonds reinforcing stacking of TPE-FF into 2D sheets via hydrogen bonding and C–H···π interactions. The unit cell formed by the tetramers using periodic boundary conditions revealed an end-to-end distance corresponding to the GIXD peak at 2θ = 1.16° (Fig. 3f). The height of 1.4 nm of the unit-cells corroborated with that from the GIXD peak at 2θ = 9.4°. Notably, the unit cell dimension for ǀθǀ = 111º reduces in comparison to ǀθǀ =157° owing to the stronger intermolecular interactions, although the height of the unit cells remains the same for both the conformations. The repetition of the unit cells along the crystallographic directions produced the 2D sheets that was stabilized by hydrogen bonds, C–H···π interactions and face-to-face π–π interactions between aromatic rings as reported in other organic crystals.³⁴

Given the crystalline nature of the SMWs and the 2D molecular sheets, their optical absorption and photoluminescence (PL) spectra were next examined (Fig. 4a and 4b). The absorption spectra of SMW and 2D molecular sheets showed broad peaks at ~ 310 nm in the UV region corresponding to π–π* transition (Fig. 4a).⁴⁷ The absorbance increases for the 2D molecular sheets in comparison to the SMWs. The PL spectra displayed a broad peak at ~ 467 nm in the visible region (Fig. 4b). The PL intensity was significantly larger for the 2D molecular sheets compared to that of the SMW. Both 2D sheets and SMWs exhibited the same PL peak position irrespective of the excitation wavelength. Confocal laser fluorescence microscopy (CLFM) imaging of the SMWs and 2D molecular sheets confirmed cyan colored emission corresponding to the PL peak position in the visible region (Fig. 4c and 4d). Bright fluorescent uniform thumb-shape domes of the SMWs similar to the AFM images were observed at ǀθǀ = 157º

(Fig. 4c). The CLFM image at the ǀθǀ =111° showed large area 2D molecular sheets with intense cyan colored emission (Fig. 4d). It is important to understand the key role of TPE and FF moieties on the molecular packing within the observed supramolecular assemblies. Clearly, the interaction of FF with the flexible TPE depending on its conformation is a major driving force. Based on this concept, we further employed Perylene-FF (Fig. 4e) where the flexible propeller shaped TPE group is replaced by a rigid planar perylene moiety (compound 2, see SI for the details of synthesis and characterization). Notably the π−A isotherm of Perylene-FF on water surface did not exhibit any plateau region (blue curve in Fig. 1) suggesting that the plateau originated owing to the presence of flexible non-planar TPE ‘handle’ of TPE-FF. The corresponding AFM image showed the presence of close packed bundles of long fibers (Fig. 4g). The fibrous morphology of Perylene-FF is in contrast with the SMWs or 2D molecular sheets formed by TPE-FF. Furthermore, the role of FF on the observed supramolecular assembly was further examined by synthesizing TPE-AA where the phenylalanines in FF moiety were substituted by the alanine (AA) (Fig. 4f). For the details of synthesis and characterization of compound of 3, TPE-AA, see Scheme S1. The π−A isotherm of TPE-AA on water surface showed only an inflection point near 13 mN m^− 1 instead of exhibiting a plateau region like TPE-FF (Figure S18). Resultant AFM morphology showed globular shaped aggregates at low compression which has a clear tendency to assemble into ring shaped morphology via merger of the globules at higher compression (Fig. 4h, Figure S19). The assembly exhibited by TPE-AA is clearly different from the assembly formed by the TPE-FF. These control systems via changing the end groups synthetically strongly established the morphological transformation from SMWs to 2D sheets by the interaction of flexible propeller shaped TPE and FF groups through the change in ǀθǀ of FF moiety aided by the compression at the water surface.

We further recorded the Circular Dichroism (CD) spectra to examine the effect of the morphological transformation of TPE-FF from the SMWs to the 2D molecular sheets. The CD spectra of TPE-FF exhibited positive and negative Cotton effects at 204 and 246 nm respectively indicating a β-sheets rich structure for the SMWs at higher ǀθǀ = 157° (Fig. 5a).^{48, 49, 50} The broad negative peak at 331 nm indicated a strong π−π stacking of phenyl rings creating a highly asymmetric environment for the strong twists of the β-sheet structure. In fact, such a twisted structure was evidenced from the higher resolution AFM image of the SMWs (Figure S20).⁵⁰ Interestingly, one positive peak at 195 nm and two negative peaks at 211 and 231 nm corresponding to α-helix structure appeared in the CD spectrum of the 2D sheets at lower ǀθǀ = 111º (Fig. 5b). Notably, the peaks corresponding β-sheet conformation were absent in the CD spectrum of the 2D sheets. This observation demonstrates a one-step secondary structure transformation from β-sheet to α-helix at the flat-water surface upon morphology transformation from SMW to 2D molecular sheets. In contrast, the drop-casting of TPE-FF solution at different concentrations showed undetectable CD signal corresponding to the non-helical conformation of the rings (Fig. 5c and Figure S17f). We predict that TPE-FF remains at ǀθǀ = 90º in the dilute solution phase giving rise to the formation of ring shape morphology which is again in agreement with the simulated morphology observed by Xiong et al.⁴⁴ On the other hand, Perylene-FF displayed positive CD peaks at 196, 214 and 259 nm which correspond to the random coil structure while β-sheet or α-helix structures were completely absent in this case (Fig. 5d).

To confirm the transformation of the secondary structure, solid-state FTIR spectra of the SMWs and 2D molecular sheets were recorded. The SMWs displayed amide A bands in the ~ 3400–3200 cm^− 1 region owing to N − H stretching vibrations (Figure S21).^{51, 52, 53} Specifically, the amide A bands appeared at 3210 cm^− 1, 3225 cm^− 1, 3245 cm^− 1, 3267 cm^− 1, 3300 cm^− 1 and 3324 cm^− 1 for the SMWs whereas the peaks at 3225 cm^− 1 and 3267 cm^− 1 were absent for the 2D molecular sheets. To mention, the non-hydrogen bonded N − H corresponds to higher energy bands and the intramolecular hydrogen bonded N − H corresponds to the lower energy bands.^{54, 55} The FTIR spectra clearly indicate that the intramolecular hydrogen bond interactions between the amide groups are altered due to the morphology transformation from the SMWs to the 2D molecular sheets. Moreover, the splitting of amide A band at 3324 cm^− 1 indicated a different pattern of intramolecular hydrogen bonding interactions between the amide groups. Such a change in the intramolecular hydrogen bond interaction facilitates the conformational change of TPE-FF on water surface resulting in the unprecedented transformation of β-sheet to α-helix secondary structure. The 1800 − 500 cm^− 1 region corresponds to the stretching band of amide I (vibration of C = O) and the bending band of amide II (C–N stretching and in-plane vibration of N − H) (Fig. 5e).^{53, 54} Additionally, 2D molecular sheets showed intense and sharper amide II bands (1558, 1540, and 1507 cm^− 1) compared to that of the SMWs implying restricted C–N stretching and in-plane vibration of N − H bonds (Fig. 5e). We analyzed the amide I region corresponding to the stretching mode of C = O groups to identify the types of secondary structures. The SMWs showed stretching bands of β-sheets (1600 cm^− 1) and anti-parallel β-sheets (1684 cm^− 1) along with the α-helical conformation (1653 cm^− 1) (Fig. 5e, Table S2).⁵⁶ Other secondary structures like random coils and turn structures were however, not prominent in the assembled SMWs. Interestingly, the 2D molecular sheets displayed a broad peak at 1650 cm^− 1 corresponding to the α-helix conformation, while the β-sheets peaks disappeared completely (Fig. 5e, Table S2). Further, we quantified the proportion of β-sheet and α-helix structures by fitting the peaks in the amide I region ranging from 1600 to 1700 cm^− 1 (Fig. 5f).⁵⁷ The SMWs contained ~ 84% of β-sheet, ~ 7% of antiparallel β-sheet along with ~ 9% α-helix conformation (Table S2). However, a complete 100% transition from β-sheet to α-helix was observed for the 2D molecular sheets showing only a broad peak at 1650 cm^− 1 corresponding to α-helix structure (Table S2). This observation univocally proves a complete secondary structural transformation from the β-sheets to α-helix conformation in one-step at the water surface upon compression of TPE-FF using a propeller-like handle in the dipeptide. This is the first demonstration of such unequivocal transformation of secondary structure of FF based self-assemblies thus formed which share key structural features with the amyloids.

In summary, we demonstrate herein the tailor-made self-assembly of aromatic-rich dipeptides into distinct architectures on the water surface. Two different morphologies including the SWMs and the 2D molecular sheets with distinct secondary structures are formed upon compression at the water surface. The well-ordered supramolecular assemblies in the crystalline states showed the presence of a closely packed network of TPE-FF reinforced with extensive hydrogen bonding and C–H···π interactions. We explored the influences of the conformational complexity with the molecular packing associated with self-assembled structures as well as the assembly dynamics. We found that the dihedral angle between the phenyl rings of FF dictated the conformations of the self-assembly into β-sheet and α-helix. First, the SMWs in β-sheet structure is formed with larger dihedral angle, which completely transformed into α-helix in 2D sheets with smaller dihedral angle. The change in the dihedral angle also alters the hydrogen bond length and binding energies of the β-sheet and α-helix structures. A combination of optical measurements, including CD and FTIR spectroscopy, further corroborate the complete transformation of secondary structure from the β-sheet to α-helix comprehensively. These finding provide a totally new perspective in understanding the role of supramolecular assembly in the secondary structure formation and its subsequent complete transformation. The unprecedented control achieved in transforming β-sheet to α-helix provide useful insights toward designing new drugs that may induce such structural conversion to alleviate amyloid formation which is widely manifested in several physiological disorders.

Acknowledgements

The authors thank J C Bose grant (to SB) SERB-STAR grant #STR/2020/000053 (to SA) for the financial support.

Gazit, E. Self-assembled peptide nanostructures: the design of molecular building blocks and their technological utilization. Chem. Soc. Rev. 36, 1263-1269 (2007).
Tao, K., Makam P., Aizen, R. & Gazit, E. Self-assembling peptide semiconductors. Science 358, eaam9756 (2017).
Vella, F. Introduction to protein structure. By C Branden and J Tooze. pp 302. garland publishing, New York. 1991 ISBN 0–8513–0270–3 (pbk).). Wiley Online Library (1992).
Ji, W., Yuan, C., Chakraborty, P., Gilead, S., Yan, X. & Gazit E. Stoichiometry-controlled secondary structure transition of amyloid-derived supramolecular dipeptide co-assemblies. Commun. Chem. 2, 65 (2019).
Adamcik, J. & Mezzenga, R. Amyloid polymorphism in the protein folding and aggregation energy landscape. Angew. Chem. Int. Ed. 57, 8370-8382 (2018).
Stefani, M. & Dobson, CM. Protein aggregation and aggregate toxicity: new insights into protein folding, misfolding diseases and biological evolution. J. Mol. Med. 81, 678-699 (2003).
Knowles, T. P., Vendruscolo, M. & Dobson, CM. The amyloid state and its association with protein misfolding diseases. Nat. Rev. Mol. Cell Biol. 15, 384-396 (2014).
Xu, Y. et al. Conformational transition of amyloid β-peptide Proc. Natl. Acad. Sci. U.S.A 102, 5403-5407 (2005).
Wang, S.-T. et al. Sequence-dependent self-assembly and structural diversity of islet amyloid polypeptide-derived β-sheet fibrils. ACS Nano 11, 8579-8589 (2017).
Dong, J., Shokes, J. E., Scott, R. A. & Lynn, D. G. Modulating amyloid self-assembly and fibril morphology with Zn (II). J. Am. Chem. Soc. 128, 3540-3542 (2006).
Ghosh, G., Barman, R., Mukherjee, A., Ghosh, U., Ghosh, S. & Fernández, G. Control over multiple nano‐and secondary structures in peptide self‐assembly. Angew. Chem. Int. Ed. 61, e202113403 (2022).
Umesh, Bera, S. & Bhattacharya, S. Dual Circularly Polarized Luminescence (CPL) and Piezoelectric Responses in Self‐Assembled Chiral Nanostructures Derived from a Dipeptide Based Piezorganogel. Small, 2308104 (2023).
Pochan, D. J., Schneider, J. P., Kretsinger, J., Ozbas, B., Rajagopal, K. & Haines, L. Thermally reversible hydrogels via intramolecular folding and consequent self-assembly of a de novo designed peptide. J. Am. Chem. Soc. 125, 11802-11803 (2003).
Singh, A., Joseph, J. P., Gupta, D., Miglani, C., Mavlankar, N. A. & Pal, A. Photothermally switchable peptide nanostructures towards modulating catalytic hydrolase activity. Nanoscale 13, 13401-13409 (2021).
Maiti, B., Bhattacharjee, S. & Bhattacharya, S. Perfluoroarene induces a pentapeptidic hydrotrope into a pH-tolerant hydrogel allowing naked eye sensing of Ca 2+ ions. Nanoscale 11, 2223-2230 (2019).
Moitra, P., Kumar, K., Kondaiah, P. & Bhattacharya, S. Efficacious Anticancer Drug Delivery Mediated by a pH‐Sensitive Self‐Assembly of a Conserved Tripeptide Derived from Tyrosine Kinase NGF Receptor. Angew. Chem. Int. Ed. 53, 1113-1117 (2014).
Kumar, K., Moitra, P., Bashir, M., Kondaiah, P. & Bhattacharya, S. Natural tripeptide capped pH-sensitive gold nanoparticles for efficacious doxorubicin delivery both in vitro and in vivo. Nanoscale 12, 1067-1074 (2020).
Ramadan, D., Cline, D. J., Bai, S., Thorpe, C. & Schneider, J. P. Effects of As (III) binding on β-hairpin structure. J. Am. Chem. Soc. 129, 2981-2988 (2007).
Ji, W. et al. Metal-ion modulated structural transformation of amyloid-like dipeptide supramolecular self-assembly. ACS Nano 13, 7300-7309 (2019).
Mimna, R., Camus, M.-S., Schmid, A., Tuchscherer, G., Lashuel, H. A. & Mutter, M. Disruption of amyloid-derived peptide assemblies through the controlled induction of a beta-sheet to alpha-helix transformation: application of the switch concept. Angew. Chem. Int. Ed. 46, 2681-2684 (2007).
Ozbas, B., Kretsinger, J., Rajagopal, K., Schneider, J. P. & Pochan, D. J. Salt-triggered peptide folding and consequent self-assembly into hydrogels with tunable modulus. Macromolecules 37, 7331-7337 (2004).
Li, J., Du, X., Hashim, S., Shy, A. & Xu, B. Aromatic–aromatic interactions enable α-helix to β-sheet transition of peptides to form supramolecular hydrogels. J. Am. Chem. Soc. 139, 71-74 (2017).
Ji, W. et al. Coassembly-induced transformation of dipeptide amyloid-like structures into stimuli-responsive supramolecular materials. ACS Nano 14, 7181-7190 (2020).
Gupta. D. et al. Enzyme-responsive chiral self-sorting in amyloid-inspired minimalistic peptide amphiphiles. Nanoscale 12, 18692-18700 (2020).
Singh, A., Joseph, J. P., Gupta, D., Sarkar, I. & Pal, A. Pathway driven self-assembly and living supramolecular polymerization in an amyloid-inspired peptide amphiphile. Chem. Commun. 54, 10730-10733 (2018).
Görbitz, C. H. The structure of nanotubes formed by diphenylalanine, the core recognition motif of Alzheimer's β-amyloid polypeptide. Chem. Commun., 2332-2334 (2006).
Reches, M. & Gazit, E. Casting metal nanowires within discrete self-assembled peptide nanotubes. Science 300, 625-627 (2003).
Reches, M. & Gazit, E. Controlled patterning of aligned self-assembled peptide nanotubes. Nat. Nanotechnol. 1, 195-200 (2006).
Frisch, M. et al. Gaussian, Inc., Wallingford CT, 2009.
Wang, Y. et al. Manipulating the Piezoelectric Response of Amino Acid-Based Assemblies by Supramolecular Engineering. J. Am. Chem. Soc. 145, 15331-15342 (2023).
Yuan, H. et al. Modified Stranski–Krastanov growth of amino acid arrays toward piezoelectric energy harvesting. ACS Appl. Mater. Interfaces 14, 46304-46312 (2022).
Gupta, D., Gupta, V., Nath, D., Miglani, C., Mandal, D. & Pal, A. Stimuli-responsive self-assembly disassembly in peptide amphiphiles to endow block-co-fibers and tunable piezoelectric response. ACS Appl. Mater. Interfaces 15, 25110-25121 (2023).
Hauser, C. A., Maurer-Stroh, S. & Martins, I. C. Amyloid-based nanosensors and nanodevices. Chem. Soc. Rev. 43, 5326-5345 (2014).
Li, Q., Jia, Y., Dai, L., Yang, Y. & Li, J. Controlled rod nanostructured assembly of diphenylalanine and their optical waveguide properties. ACS Nano 9, 2689-2695 (2015).
Gazit, E. Self assembly of short aromatic peptides into amyloid fibrils and related nanostructures. Prion 1, 32-35 (2007).
Rao, K. et al. Transparent, flexible MAPbI 3 perovskite microwire arrays passivated with ultra-hydrophobic supramolecular self-assembly for stable and high-performance photodetectors. Nanoscale 12, 11986-11996 (2020).
Zhao, Y., Wu, Y., Yan, G. & Zhang, K. Aggregation-induced emission block copolymers based on ring-opening metathesis polymerization. RSC Adv. 4, 51194-51200 (2014).
Yan, X., Li, J. & Möhwald, H. Self‐assembly of hexagonal peptide microtubes and their optical waveguiding. Adv. Mater. 23, 2796-2801 (2011).
Yan, X., He, Q., Wang, K., Duan, L., Cui, Y. & Li, J. Transition of cationic dipeptide nanotubes into vesicles and oligonucleotide delivery. Angew. Chem. Int. Ed. 46, 2431-2434 (2007).
Paramonov, S. E., Jun, H.-W. & Hartgerink, J. D. Self-assembly of peptide− amphiphile nanofibers: the roles of hydrogen bonding and amphiphilic packing. J. Am. Chem. Soc. 128, 7291-7298 (2006).
Liu, L., Klausen, L.H. & Dong, M. Two-dimensional peptide based functional nanomaterials. Nano Today 23, 40-58 (2018).
Khoe, U., Yang, Y. & Zhang, S. Self-assembly of nanodonut structure from a cone-shaped designer lipid-like peptide surfactant. Langmuir 25, 4111-4114 (2009).
Black, M., Trent, A., Kostenko, Y., Lee, J. S., Olive, C. & Tirrell, M. Self‐assembled peptide amphiphile micelles containing a cytotoxic T‐cell epitope promote a protective immune response in vivo. Adv. Mater. 24, 3845-3849 (2012).
Xiong, Q., Jiang, Y., Cai, X., Yang, F., Li, Z. & Han, W. Conformation dependence of diphenylalanine self-assembly structures and dynamics: Insights from hybrid-resolution simulations. ACS Nano 13, 4455-4468 (2019).
Zhu, P., Yan, X., Su, Y., Yang, Y. & Li, J. Solvent‐induced structural transition of self‐assembled dipeptide: from organogels to microcrystals. Chem. Eur. J. 16, 3176-3183 (2010).
Andrade-Filho, T., Martins, T. C., Ferreira, F. F., Alves, W. A. & Rocha A. R. Water-driven stabilization of diphenylalanine nanotube structures. Theor. Chem. Acc. 135, 1-8 (2016).
Birks, J. B. Photophysics of aromatic molecules. Wiley-Interscience (1970).
Wang, Y. et al. Rational design of chiral nanostructures from self-assembly of a ferrocene-modified dipeptide. J. Am. Chem. Soc. 137, 7869-7880 (2015).
Lara, C., Reynolds, N. P., Berryman, J. T., Xu, A., Zhang, A. & Mezzenga, R. ILQINS hexapeptide, identified in lysozyme left-handed helical ribbons and nanotubes, forms right-handed helical ribbons and crystals. J. Am. Chem. Soc. 136, 4732-4739 (2014).
Xie, Y. et al. Electrostatic and aromatic interaction-directed supramolecular self-assembly of a designed Fmoc-tripeptide into helical nanoribbons. Langmuir 31, 2885-2894 (2015).
Toniolo, C. & Palumbo, M. Solid‐state infrared absorption spectra and chain arrangement in some synthetic homooligopeptides in the intermolecularly hydrogen‐bonded pleated‐sheet β‐conformation. Biopolymers 16, 219-224 (1977).
Moretto, V., Crisma, M., Bonora, G., Toniolo, C., Balaram, H. & Balaram, P. Comparison of the effect of five guest residues on the. beta.-sheet conformation of host (L-val) n oligopeptides. Macromolecules 22, 2939-2944 (1989).
Kong, J. & Yu, S. Fourier transform infrared spectroscopic analysis of protein secondary structures. Acta Biochim. Biophys. Sin. 39, 549-559 (2007).
Dado, G. P. & Gellman, S. H. Intramolecular hydrogen bonding in derivatives of. beta.-alanine and. gamma.-amino butyric acid; Model studies for the folding of unnatural polypeptide backbones. J. Am. Chem. Soc. 116, 1054-1062 (1994).
Dinesh, B., Vinaya, V., Raghothama, S. & Balaram, P. C12‐Helix Development in (αγ) n Sequences–Spectroscopic Characterization of Boc–[Aib–γ4 (R) Val]–OMe Oligomers. Eur. J. Org. Chem. 2013, 3590-3596 (2013).
Xing, R., Yuan, C., Li, S., Song, J., Li, J. & Yan, X. Charge‐Induced Secondary Structure Transformation of Amyloid‐Derived Dipeptide Assemblies from β‐Sheet to α‐Helix. Angew. Chem. Int. Ed. 57, 1537-1542 (2018).
Jackson, M. & Mantsch, H. H. The use and misuse of FTIR spectroscopy in the determination of protein structure. Crit. Rev. Biochem. Mol. Biol. 30, 95-120 (1995).

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Propeller Induced Complete Transformation of the Secondary Structure of a Dipeptide on Water Surface Controlled by Chiral Supramolecular Assembly

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Propeller Induced Complete Transformation of the Secondary Structure of a Dipeptide on Water Surface Controlled by Chiral Supramolecular Assembly

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