DFT Analyses of Arsylsemicarbazone Group as Functional compound for application as excellent �uorescent probes and medicament: Study on virtual Screening through Molecular Docking

The present invention reports two novel functional compounds, 2-hydroxy-3-naphthaldehyde thiosemicarbazone (2H3NTS) and 2-hydroxy-3-naphthaldehyde semi carbazone (2H3NS) as an excellent �uorescent probe which possess anticancer features and are not yet synthesized by any research group. The DFT study reveals signi�cantly higher stokes shift (315 nm) for 2H3NS indicating swift relaxation from initial to the emissive state and reduces self-quenching from self-molecular absorption which favours its practical application. Consequently, successive in-vitro activity of 2H3NTS and /2H3NS is studied using molecular docking towards the inhibition capacity of target kinase protein like CDK, primarily responsible for cell growth. As expected, 2H3NS is capable of binding both competitive ATP binding SITE I and non-competitive SITE II which lies below the T-loop, thereby inhibiting the cell growth and differentiation. However, 2H3NTS with polarizable sulphur is incapable of binding at SITE I with selective inhibition posing the ATP site to be well conserved.


Introduction
The research area pertaining to photochemistry of numerous functional compounds is signi cantly important owing to the tuning of photo physics through photoexcitation.The sensors and imaging applications based on uorescence are routinely used in environmental science, biology, chemistry, point of care application, pharmacology etc [1].The implementation of uorescent probe has enabled the application and initiation of research and development towards the physiological and pathological process which are effective towards the detection of environmental pollutants in either aqueous or air media.However, the limitation lies in the sensitivity and selectivity of the process and the imposed actions by regulatory bodies which restrict practical application of certain probes for real time setting [2].
The probes based on uorescence employ either selective host-guest interaction or speci c chemical reaction affecting the uorescence properties of the system [3].Presence of non-covalent and reversible interaction among host and guest generates chemo sensing probes [4a, 4b].The primary mechanisms studied for uorescence mechanism viz.a) photoinduced electron transfer (PET), internal charge transfer (ICT), Forster Resonance Energy (FRET) etc. [5][6][7] are studied throughout the globe.In this connection, excited state intramolecular proton transfer (ESIPT) is highly effective and important in terms of application of such probes for multifaceted purpose like detection of biologically or environmentally important species.The primary criteria for selecting an active ESIPT uorescence molecule are the presence of a hydrogen bond donor (-NH 2 and -OH) and a hydrogen bond acceptor (-COO and QN-) [8-9].
ESIPT is an example of four level photochemical process which initiates with the electronic enol ground state as shown in Fig. 1.The electronic charge of such active molecule gets redistributed upon photoexcitation thereby generating greater acidity in hydrogen donar group and basicity for hydrogen acceptor group [8][9].Consequently, enol to keto phototautomerization results of the order 10 -12 sec -1 .In this context, naphthalene acts as an excellent chromophore wherein stable six membered intramolecular hydrogen ring is accessible due to the presence of two distinct non-equivalent positions of carbon pair [10][11][12] which is shown in Fig. 1.The ndings are corroborated with FTIR spectroscopy through the formation of both O-H and -N-H bond in the transition state.
Among numerous uorescence active probes, arsylsemicarbazone is a group of chemicals which are studied for ESIPT.The mentioned crystalline parent homologue is utilized for the identi cation of higher homologues of aldehyde and ketones by melting point analyses.Fetoh et al reported the biological and analytical study on 2-hydroxy-1 -naphthaldehyde thiosemicarbazone.The photophysical properties of the mentioned substituted thiosemicarbazone is further tailored using d-block metals like Pd (II), Cu (II) and Ru (III) [13].The e cacy of such derivatives as medicament like antimicrobial activity through chelation (binding) within affected cells using transition metals like Fe and Cu has also been reported [14][15][16].The semicarbazone derivative of 2-hydroxy-1-naphthaldehyde shows its inhibitory mechanism and kinetics with respect to jack bean urease [17].The derivatives also play a potent role in the pharmaceutical application as exhibited through bactericidal action against E. coli, B. subtilis, and S. aureus [18].Ganorkar et al further reported E)-1-(4-(diethylamino)-2-hydroxybenzylidene)-4,4-dimethylthiosemicarbazide (DAHTS) as an e cient bioactive pharmacophore which is a Schiff base derivative [18] and is validated using electronic absorption, steady state, time resolve uorescence spectroscopic technique and theoretical DFT analyses.The mentioned derivative of thiosemicarbazone is proved to be a bioactive medicament using both the results from experimental tools and theoretical DFT study, on comprehensive synthetic and photophysical aspects.Therefore, functionalization of the arsylsemicarbazone group imparts the speci c role towards applicability as an effective medicament and the same could be studied using photophysical process.
In the context of aforementioned literature survey, two newer uorescence probes are designed viz.2hydroxy-3-naphthaldehyde thiosemicarbazone (2H3NTS) and 2-hydroxy-3-naphthaldehyde semi carbazone (2H3NS).To the best of knowledge of the inventors, the stated compounds are not yet reported by any research group.The primary objective of the present article is to establish the e cacy of both 2H3NTS and /2H3NS as medicament towards anti-cancer/anti-in ammatory effect.The article intends to establish on the role of these mentioned systems towards the inhibition of cell growth through molecular docking with targeted Cyclin-dependent kinase 2 (CDK2) group of protein.In this connection, the reactivity and role of functionalization on the compounds are studied using density functional theory (DFT).DFT has been undertaken in order to explore the excited state intramolecular proton transfer (ESIPT) of the two mentioned probes.In conjunction, the effectivity of the stated compounds in terms of anti-cancer agent is theoretically screened through molecular docking study with CDK protein.Before proceeding for the in vivo experimental approach, a theoretical screening is highly signi cant in establishing the tentative e cacy of the parent systems wherein the in uence of functionalization could be well studied using DFT.In absence of such screening, structure-based designing of drug is not possible.Molecular docking is capable of exhibiting the prediction of possible binding conformation of small molecules like 2H3NS/2H3NTS with targeted binding site within protein.

Computational Details
Density functional theory (DFT) utilize the electron cloud which is spatially dependent.Study of many body system is however complex and are identi ed using functionals [19][20][21].In contrast to the electronic structure methods of computation, DFT utilizes one body density as the fundamental variable.
In this aspect, owing to the fact that density n (r) is a functional of three coordinates, DFT is capable of computing many bodies (large) system provided system integration is optimum.
In the present context, the calculations for ground and excited states have been carried out using Gaussian 03 module and the structures were generated by Gauss View 5.0 [22].The basis set of 6-31G* was engaged for optimization of ground state geometry of both 2H3NS and 2H3NTS using DFT.Furthermore, using B3LYP hybrid functional, the geometry optimization was implemented.The potential energy curve is computed in the range of 0.7-2.6A˚ for pre-set O-H distances for understanding the process of intramolecular proton transfer process (using B3LYP/6-31G*) [23].Unlike, the optimization for ground state, TDDFT/B3LYP/6-31G* is utilized for excited state optimization for the mentioned systems.The corresponding energy of the excited state (E j ) is obtained using E j = E g + E i→j (where, i and j are the orbital notations corresponding to occupied ground state and vacant ground state) [24][25].Structures of 2-hydroxy-3-naphthaldehyde thiosemicarbazone [2H3NTS] and 2-hydroxy-3-naphthaldehyde semicarbazone [2H3NS] is optimized using rst principal quantum calculations.Both 2H3NTS and 2H3NS undergoes intramolecular proton transfer (Fig. 2) which is even replicated during geometry optimized in Gaussian.The schematic for ESIPT mechanism is described in Fig. 3 for 2H3NS considering 2H3NS as an example which involve both tautomer's.In uence of elements (of similar group having variation in polarizability and electron cloud distribution) is studied on the in-silico activity using the target kinase protein viz CDK2.
Correlation is established on the comparative in vitro activity of both 2H3NTS and / 2H3NS towards the inhibition capacity of CDK protein system, primarily responsible for cell growth and differentiation.In this aspect, an initial screening study is reported on both 2H3NTS and 2H3NS with serum albumin like bovine serum albumin (BSA).Molecular docking is carried out with BSA and CDK2 (PDB entry ID: 4F5S and 5NEV; https://www.rcsb.org/structure/).Post geometry optimization, the PDB structure of parent systems were generated by Gauss View 5.0.The respective simulations done during docking were undertaken and analysed by SWISSDOCK and UCSF Chimera respectively [26][27].The analyses were done based on the magnitude of spontaneity factor, tness parameter and other details discussed in the subsequent section.

In uence of substitution on DFT analyses
The interesting feature of the parent 2H3NTS and /2H3NS is the capability proton transfer as exhibited in Fig. 3.The phenomena of ESIPT are favourable when the extent of formation of tautomerism through hydrogen migration is accelerated in the excited state.This is dependent on the position of migratory hydrogen in the target system which tend to favour the intramolecular hydrogen bond formation which is exempli ed in Fig. 2. In this context, potential energy curves (PEC's) for either enolic and tautomeric forms are simulated using DFT, for determination of intermolecular O-H bond distance.The computation involves S1, S2 (two singlet excites states) and T1 ( rst excited triplet state).The feasibility of excited state intramolecular proton transfer occurs among a donor of proton containing either an -OH or -NH group and an acceptor compatible to said donor system [28].In such context, validation such transfer of proton is undertaken using DFT in terms of variation in the angle of O-H----N, wherein the geometry of transition state is signi cant and account for the validation of the said transformation.As stated in the aforementioned section, TDDFT/6-31G* is employed for computation of GSIPT plots and its energetics [8][9].Figure 4 represents the potential energy curves (PEC) with respect to the states S 0 , S 1 , S 2 and T 1 .
The simulated PEC is plotted as a function of O-H distance for 2H3NS.The potential energy curve for both 2H3NS (Fig. 4) and 2H3NTS [29] clearly represent the phenomena of ESIPT involved within two mentioned tautomer's viz keto and enol and thereby results in endothermicity.The intramolecular reaction favors the thermodynamic process in lowest existed S 1 and T 1 states ans shows exothermicity.Therefore, compared to the ground state, the activation barrier for proton transfer process is favourable in excited state.In this respect, 2H3NS exhibits a stokes shift of 315 nm which enables it for effective usage as uorescent probes.Similarly, the stokes shift of 156 nm is reported for H3NTS by Akash et al [29].
Though the R O−H magnitude for both the systems are similar, however, the trend of potential energy curve as a function of O-H bond is variable.This is primarily due to the in uence of substitutions speci cally oxygen and sulphur.A large stokes shift is noted specially for 2H3NS which indicate relatively easy and swift relaxation from the initial state to the emissive state.Therefore, during experimentation in due course for establishing the capability of medicament, interaction study could be easily undertaken using photophysical process mentioned herein.
In order to exemplify the formation of bonds in either enol, keto and TS, FTIR spectra is simulated for 2H3NTS and is reported in our earlier communications [29].The simulation of enol form of 2H3NTS generates a sharp peak of FTIR at 3450 cm − 1 which corresponds to the stretching of O-H which is absent in the keto form.As expected, the enol tautomer does not the formation of any N-H bond which is evident in the respective keto form.The transformation to keto-enol conversion or vice versa is found to comprise of a transition state wherein partial hydrogen bond formed with N-while connecting with O-attached to ortho carbon atom (studied through simulated FTIR study).In addition to the identi cation of functional groups like O-H and N-H, unsaturated groups are also noted from the FTIR spectrum.FTIR peaks are identi ed at 1600 cm − 1 (enol and TS state) and 1221-1228 cm − 1 (in enol, keto and TS form) which corresponds to -C = N group and -C = S stretching vibration respectively.2H3NTS shows the presence of -C-C-, -C-O-and -C-N-functionalities through the nger print region marked in the lower frequency region.
Similar observation is outlined for 2H3NS system as shown in Fig. 5.
As per the functionality, the respective bond identi cations are marked in enol, keto and transition state.
The respective peak frequencies of -C = N is clearly observed in both enol and keto conformation without any indication in the transition state.The TS shows the N-H stretching frequency supporting the form as shown in the inset gures.The electronic structure of the systems in terms of keto enol transformation is simulated using Density functional theory.The con guration of frontier molecular orbitals (FMO) for keto, enol and transition state for 2H3NTS is reported by Akash et al [29] in the earlier communication.The thermodynamic energetics using frontier molecular orbital approach is shown in Fig. 6-8 which represent pictorial form of molecular orbitals viz.HOMO, LUMO con gurations for enol, keto tautomer along with the transition state.
The positional aspect of electron cloud resulted owing to dynamic orbital micing is well understood and implemented towards analysis of chemical reactivity and kinetic activity of the target functional system.
Concentrated electronic zone is marked through red and de cient zone using green colour code.The systems mentioned here does not show any degenerate level of energy state among LUMO and LUMO + 1/2.The earlier communication [29] reported the migration of charge distribution from enol to keto form in the HOMO of 2H3NTS.Upon tautomerization from enol to keto form, the distributed charge onto phenyl ring (along with O-H functionality) is found to shift towards the nitrogen centre which is clearly evident from the orbital con guration.
In contrast, replacement of Sulphur group by oxygen in 2H3NS is found to generate distributed charge density.It is observed that, extended electron distribution (in terms of electronegative (red) and electropositive (green) is present in HOMO of enol, TS and keto form.Owing to such distributed cloud, energy band diagram is also provided for each system in 2H3NS (Fig. 6-8).Sulphur being more polarizable compared to oxygen, a sharp variation in the electron cloud is noted from enol to keto from through TS.Presence of oxygen atom in place of sulphur in 2H3NS generates a more symmetric electronic cloud with alternate distribution of charge with more negative FMO energy compared to 2H3NTS system.The comparative energy gap (ΔE LUMO−HOMO ) shown in Fig. 6-7 shows favourable transformation from enol to keto form in the ground state (S o ).Hence, such spontaneous conversion allows favourable probability for ESIPT of 2H3NTS and 2H3NS at excited energy state.On a similar note, the orbital con guration of LUMO signi es the charge acceptance probability, which depicts the distribution of charge on the total system.These observations validate the positive feasibility of proton transfer in the excited state.Hence, the FMO study establishes the variation of reactivity as a function of substitution in either of the systems considered.This is correlated with the interaction of these system with protein for usage as medicament.
The density of states (DOS) plots for 2H3NTS and 2H3NS are represented as a function of spin states viz α and β respectively.The presented DOS represent the distribution from − 20eV till conduction regime (positive energy) highlighting fermi energy (E F ) as the reference.Figure 9 represent almost similar pattern of DOS for tautomer's of 2H3NTS with a common principal energy regime.However, it could be noted that the extent of overlapping in the transition state is more above fermi energy as indicated by lesser nodal regions.This signi es simultaneous formation of partial hydrogen bonds with either O-and / N-site within the system.Hence, the DOS of transition states exhibits both the nature /traits of enol and keto form.In contrast to 2H3NTS system [29] exhibiting a wide conduction regime (till 120 eV), a spread of only 30 eV is considered in 2H3NS system, since it could be visible that understanding on nature of energy distribution could be well studied till 30 eV conduction range.The valence band in the enol form 2H3NTS [29] shows a sharp peak at -5.5 eV which however observed to get shifted for keto form with a broad hump.
However, in 2H3NS system, the symmetric electron cloud distribution (as visible from FMO) is clear from the reduction in nodal region after − 15 eV.2H3NTS is observed to exhibit intrinsic variability due to the shifting of electron density from O-H group of enol towards the N-H group in keto and transition state which is evident from the presence of non-nodal regions.The ndings from DOS are further supported by by electrostatic potential maps (Fig. 10) that exhibits the electron distribution throughout the structure.
Red moieties indicate the higher electron density region whereas the blue region signi es electron de cient zone.In this aspect the external attack for a nucleophile or electrophile could be well studied using such EPM imaging patterns.The electron contours generated on the distribution of Ground state HOMO and LUMO of the systems clearly shows visualization of the 3D sphere of in uence as a 2D map.
Compared to Sulphur, insertion of oxygen at the functionalised position allows better overlapping as observed from green cloud onto adjacent C-N segment.The green marker in EPM indicates the location of the mean potential being of electronegativity limits.Similarly, yellow regime marks the potential positions within green and electronegative red zone.Marked difference is noticed among the HOMO of 2H3NTS and 2H3NS.More polarizable functionality (Sulphur) induces broad sphere of charge as shown through the contour, however, no signi cant orbital contribution is signi ed for the adjacent carbon, nitrogen species.In contrast, replacement with oxygen tend to include the orbital coherency as observed from either FMOs in Fig. 10b.Therefore, the reported study on DFT establishes both 2H3NTS and 2H3NS potential as e cient orescence probe.However, functionalization of Arsylsemicarbazone with oxygen is studied to exhibit almost double stokes shift compared to sulphur driven functionalization.This enables 2H3NS for practical application through reducing self-quenching which results from self-molecular absorption.Hence, DFT expects 2H3NS to be a better medicament towards inhibition of CDK group of proteins.In continuation, the study is signi cant for engagement of these active functional compounds for interaction with macromolecule like protein (s) as described in subsequent section.

Molecular Docking analyses
The rst step in designing any Active Pharmaceutical Ingredient or drug design is to establish the binding with serum albumin proteins.For decades it has remained a standard protocol to study the binding interaction of selective ligands, drugs, small systems with targeted proteins [30][31].Experimentally, electrochemical technique, high-performance liquid chromatography, in addition to circular dichroism capillary, electrophoresis and isothermal titration calorimetry are utilized to study such interaction [32].In recent years, uorescence spectroscopy has evolved as another tool for study on such binding interaction owing to its higher sensitivity, selectivity, convenience and abundant theoretical foundation.In concurrence of such experimental protocols, theoretical study based on molecular docking is undertaken by all researchers in order to have an initial screening on the selection of either ligand and the protein [1,30].As per standard protocol, molecular docking of both 2H3NTS and 2H3NS is undertaken with transport proteins viz.serum albumin as shown in Fig. 11.In both the cases spontaneous binding is observed with serum albumin (ΔG 2H3NS − BSA ~ 7.38 kcal/mol; G 2H3TNS − BSA ~ 7.91 kcal/mol).The magnitude of free energy shows lesser selectivity in the interaction of bovine serum albumin (BSA) to either 2H3NTS and 2H3NS.The two systems, therefore, could be well docked with serum albumin protein.This is especially signi cant for experimental research of the reported compounds towards protein interaction.
Arsylsemicarbazone group of compounds are previously reported as effective anticancer agents having profound activity in restricting cell growth and differentiation.In this aspect, protein kinase is one of the signi cant targets of cancer treatments because they are involved in the regulation of progression, migration, proliferation, differentiation, survival an apoptosis of cell cycle [33].Presently, cancer-based research includes the interference of the drugs with DNA or key molecules necessary for cell division [27].
Present medical research is aimed at targeted therapy in order to reduce the side effects of present medicament towards the non-cancerous cells and associated so as to in uence and enhance the self-life the affected patient.In this regard, the selected target system is studied for nature of interaction with selected kinase proteins.The present context utilized semi carbazone (2H3NTS and 2H3NS) group of targets being reported of exhibiting biological properties like antimicrobial, anticonvulsant, antiin ammatory, antiproliferative, cytotoxic and pro-apoptotic.The action of acting as a protein kinase inhibition is also report for this class of drugs.It is reported that inhibition of the CDK2 and cyclin A complex results in autophagic degradation of CDK2 in cancer cells [34].Variety of CDK protein systems are reported till date with active role in cell division and growth.Hence, the drugs/chemical proposed to bear anti-cancer feasibility primarily act as an inhibitor towards the CDK function.However, 2H3NTS and 2H3NS systems are unique and such DFT and anticancer screening analyses is not reported till date by any research group.
The present study reports the molecular docking analyses of novel 2H3NTS and 2H3NS with Cyclindependent kinase 2 (CDK2) protein (Fig. 12).Based on the literature report, 13 members of 40% homology are reported in CDK family among which CDK2 is known to be superstar with known crystal structure (PDB, http://www.rcsb.org/pdb/home/home.do).Contrast to the self-functioning serum albumins, monomers of CDK are inactive and confers basal kinase activity upon interaction with speci c cyclin partners at a speci c point during cell cycle.The mode of activation of CDK systems impose conformational alterations and activate the catalytic binding pockets of the protein.Such conformational exibility plays an important role towards the regulation of signals involved in the cell growth and differentiation [35].CDK2 protein comprises primarily of three binding sites (shown in Fig. 12) among which the ATP binding pocket forms the competitive site.It could be seen that, 2H3NS results in 49 conformers during docking with ATP site (named as SITE A) with a spontaneous energy regime of -6.7 to -5.46 kcal/mol.So, effectively it could be stated that 2H3NS possess inhibitory action.However, 2H3NTS does not re ect any ATP binding a nity being composed of similar stoichiometry.In this context, it could be stated that, owing to reasonably higher conservation of the PSTAIRE helix among CDKs, for many inhibitors ATP binding site is not the perfect binding pocket.
In this aspect, presence of oxygen in 2H3NS forms it a potent inhibit upon binding with competitive site, whereas, polarisable sulphur makes 2H3NTS a selective inhibitor posing the ATP site to be well conserved.The second reported non-competitive binding SITE II lies below the T-loop (Fig. 12) and is observed to have signi cant binding con rmations with either 2H3NTS and 2H3NS.However, as per literature [35], understanding on the mechanism of ligand binding at SITE II is ambiguous and thus not marked in Fig. 12.The non-competitive groove of SITE III as per reports binds with short peptides and restricts the enzymatic activity of CDK2 by disrupting the CDK2-Cyclin complex.Zones B, C and D in Fig. 12 are the binding pockets of SITE III.
More electronegative oxygen in 2H3NS in Fig. 12a shows signi cant binding con rmers at marked B and C with more spontaneous binding at position B. The spontaneity is also supported by almost double binding conformers compared to that in position C.In contrast, the probabilistic binding conformers are almost equipoised at position C and D (Fig. 12b) owing to the presence of relatively bigger polarizable sulphur group.In both the cases, the interaction site of cyclin A is also marked which is observed to be blocked for either 2H3NTS and 2H3NS with signi cant probability.The combined study of DFT and molecular docking shows that 2H3NS with oxygen functionalization exhibits higher stokes shift (earlier section) and is capable of binding with both SITE I and SITE II of CDK2 protein.Hence, the Arsylsemicarbazone systems with more electronegative functionalization is capable of binding with competitive ATP site thereby restricting the augmentation of cell cycle.In contrast, presence of more polarization sulphur in 2H3NTS with lower stokes shift compared to 2H3NS generates asymmetric electronic cloud distribution as studied from FMO and EPM generated through DFT.It is found to be incapable of binding with completive SITE I of CDK2 and could be tested for probable medicament as anti-in ammatory agent.

Conclusions
In a nutshell, 2-hydroxy-3-naphthaldehyde thiosemicarbazone (2H3NTS) and 2-hydroxy-3-naphthaldehyde semi carbazone (2H3NS) are claimed to be novel functional compositions for utilization as anticancer/anti-in ammatory agents which are not reported as per the best of knowledge of the inventors.
In uence of elements (of similar group having variation in polarizability and electron cloud distribution) is studied on the in-silico activity for the target kinase protein viz CDK2.Correlation is established on the comparative in vitro activity of either 2H3NTS and / 2H3NS towards the inhibition capacity of CDK protein system.CDK group of protein is primarily responsible for cell growth and differentiation.For initial understanding on the pattern of reactivity, DFT study is undertaken which establishes the targeted systems, 2H3NTS and / 2H3NS as effective uorescent probes.Simulated potential energy curve (PEC) as a function of R O−H for the intra molecular proton transfer (IPT) shows higher stokes shift (315 nm) for 2H3NS compared to 157 nm (2H3NTS).This enables swift relaxation from the initial state to the emissive state for 2H3NS.Therefore, during experimentation in due course for establishing the capability of medicament, interaction study could be easily undertaken using photophysical process mentioned herein.Fronteir molecular orbital (FMO) arrangement stdied through DFT establishes that for 2H3NTS, during enol to keto transformation, the charge density is found to get shifted towards nitrogen centre and away from the phenyl rings.However, replacement of Sulphur group by oxygen in 2H3NS generates distributed charge density.The molecular approach and energetics for the conformers of 2H3NS and / 2H3NTS is studied using Frontier molecular orbital (FMO) and density of states (DOS) plots.
In connection to the observations from DFT, molecular docking study is undertaken in conjunction with two protein systems viz.bovine serum albumin (BSA) and Cyclin-dependent kinase 2 (CDK2) protein.
Both 2H3NTS and 2H3NS system are found have active inhibitory action towards the functionality of CDK2.However, the interesting aspect in this study are the positioning of the docking conformers with respect to the active sites in CDK2, which are signi cantly different for the said target systems.As expected, 2H3NS with oxygen substitution is observed to spontaneously bind with both SITE I (competitive ATP binding site) and SITE II (Non-competitive site involving t-loop) and effectively restricts the interaction of cyclin A. This signi es successful restriction of cell growth and differentiation upon utilising 2H3NS as the target drug system thereby assisting anti-in ammatory activity (like cancer growth).In contrast, 2H3NTS with sulphur substitution fails to bind with competitive ATP binding SITE -I and spontaneously bind with only non-competitive SITE II.More electronegative oxygen in 2H3NS shows spontaneous double binding conformations.In contrast, the probabilistic binding conformers are almost equipoised at non-competitive sites owing to the presence of relatively bigger polarizable sulphur group.
Though, a theoretical screening study is reported herewith, however it intends to elucidate the fundamental mechanism of selected semicarbazone derivative towards the interaction of competitive and non-completive sites in CDK2 and thus could be well undertaken for further experimentation for anticancer activity.

Declarations Figures
a ) Schematic representation of excited state intramolecular proton transfer and and b) stable ring formation using intramolecular hydrogen bond (IMHB).