Poornima Sharma

Temperature dependent Raman and DFT study of creatine.

Temperature dependent Raman spectra of creatine powder have been recorded in the temperature range 420-100K at regular intervals and different clusters of creatine have been optimized using density functional theory (DFT) in order to determine the effect of temperature on the hydrogen bonded network in the crystal structure of creatine. Vibrational assignments of all the 48 normal modes of the zwitterionic form of creatine have been done in terms of potential energy distribution obtained from DFT calculations. Precise analysis gives information about thermal motion and intermolecular interactions with respect to temperature in the crystal lattice. Formation of higher hydrogen bonded aggregates on cooling can be visualized from the spectra through clear signature of phase transition between 200K and 180K.

Multi-layered graphene quantum dots derived photodegradation mechanism of methylene blue

The photocatalytic degradation of methylene blue (MB) under visible light in the presence of a multi-layered graphene quantum dots (MLGQDs) photocatalyst has been investigated in aqueous heterogeneous solution. The photodegradation mechanism, following pseudo first order kinetics, was examined for the effects of the existing monomer (MB+)–dimer {(MB+)2} equilibrium in MB solution. The photocatalytic degradation efficiency of MB+ achieved 93.3% with a rate constant (k) of 0.056 min−1 after 60 min irradiation with green light, while less degradation ∼ 89.44% with k ∼ 0.024 min−1, was achieved for (MB+)2. MB+ is perhaps a short-lived species and favors the photodegradation of MB in comparison to the (MB+)2 species. Similar trends have been found under blue light irradiation. MB+ species easily pulls a proton from the functional groups of MLGQDs, resulting in an intermediate product Luco-methylene blue (LMB). Finally, all MB species and intermediate products degrade into an environmental benign product via highly reactive OH radicals. In addition, our ab initio theoretical results reveals that monomers abstract a proton from hydroxyl groups of MLGQDs and formation of LMB takes place, which is weakly bonded with MLGQDs by hydrogen bonds.

Spectroscopic and structural study of the newly synthesized heteroligand complex of copper with creatinine and urea.

Study of copper complex of creatinine and urea is very important in life science and medicine. In this paper, spectroscopic and structural study of a newly synthesized heteroligand complex of copper with creatinine and urea has been discussed. Structural studies have been carried out using DFT calculations and spectroscopic analyses were carried out by FT-IR, Raman, UV-vis absorption and fluorescence techniques. The copper complex of creatinine and the heteroligand complex were found to have much increased water solubility as compared to pure creatinine. The analysis of FT-IR and Raman spectra helps to understand the coordination properties of the two ligands and to determine the probable structure of the heteroligand complex. The LIBS spectra of the heteroligand complex reveal that the complex is free from other metal impurities. UV-visible absorption spectra and the fluorescence emission spectra of the aqueous solution of Cu-Crn-urea heteroligand complex at different solute concentrations have been analyzed and the complex is found to be rigid and stable in its monomeric form at very low concentrations.

Study of hydration of sarcosine, formation of its zwitterion and their different oligomers in aqueous media: a Raman spectroscopic and theoretical study.

Raman spectra of the biologically important molecule sarcosine (SAR) (C3H7NO2) were studied experimentally in aqueous solution at different concentrations. These spectra were also calculated theoretically using density functional theory (DFT) at the B3LYP/6-311++G(d,p) level. Further, all the observed normal modes were assigned through potential energy distribution (PED). Geometry optimization of SAR produced its three conformers with slightly different energies. The lowest energy conformer of SAR was selected for a systematic solvation study wherein different numbers of water molecules (nW, n=1-9) were placed near it. In the SAR-9W complex, the SAR molecule is located almost at the center of the cage of 9 water molecules. Geometries of different oligomers of SAR (dimer, trimer, tetramer and pentamer) were also optimized in aqueous media taking the input structures from crystallographic data and using the polarizable continuum (PCM). Proton transfer required for the formation of the zwitterionic form of SAR was found to occur when the number of water molecules in the first hydration shell was six or more.

Fermented papaya preparation modulates the progression of N-methyl-N-nitrosourea induced hepatocellular carcinoma in Balb/c mice.

AIM AND MAIN METHOD The medicinal properties of fermented papaya preparation (FPP) derived from Carica papaya fruit was investigated in order to determine its ability to modulate the progression of N-methyl-N-nitrosourea induced hepatocellular carcinoma in Balb/c mice. KEY FINDINGS As well as reducing the physical symptoms associated with N-methyl-N-nitrosourea (MNU)-induced hepatocellular carcinoma, supplementation of Balb/c mice with 500mg FPP/kg BW for 92days normalized the blood cell count, led to an increased activity of several key antioxidant enzymes (SOD: +20%, CAT: +81%, GPx: +66.1%, GR: +54.4%; P<0.001 vs. MNU control), increased the ferrous reducing antioxidant potential (+36.7%, P<0.001 vs. MNU control) and reduced the extent of lipid peroxidation in the liver by 44.3% (P<0.001 vs. MNU control). SIGNIFICANCE Results demonstrated the ability of FPP to preserve the integrity of liver against oxidative damage and protect hepatocytes against irreversible DNA structural modifications induced by MNU, highlighting its potential role as an immune-defense modulator during hepatocarcinoma.

Detection of in Vitro Metabolite Formation of Leflunomide: A Fluorescence Dynamics and Electronic Structure Study

The metabolic transformation of antirheumatic fluorescent drug leflunomide into its active metabolite teriflunomide through isoxazole ring opening has been monitored in vitro using steady state and time domain fluorescence spectroscopy and density functional theory. During metabolic reaction, absorption of leflunomide split into two bands resembling absorption spectra of teriflunomide. The fluorescence spectra reveal slow conversion of leflunomide to E and Z forms of teriflunomide in aqueous medium, which becomes faster at basic pH. The E form, which is more potent as a drug, becomes more stable with an increase in the basicity of the medium. Both molecules are associated with charge transfer due to twisting in the lowest singlet excited state. Excited state charge transfer followed by proton transfer was also observed in the Z form during the ring opening of leflunomide. Quantum yield and radiative decay rates have been observed to decrease for the metabolite because of an increase in nonradiative decay channels.

Surface enhanced Raman scattering based reaction monitoring of in vitro decyclization of creatinine → creatine

Creatinine → creatine decyclization is an important reaction wherein we obtain a beneficial compound from a toxic substance. Decyclization of creatinine at basic pH has been monitored in vitro by time series surface enhanced Raman scattering (SERS) using a silver island film. NH2 scissoring, CN and CO stretching modes of creatinine serve as Raman markers for monitoring the decyclization reaction. Transition state calculations using DFT have revealed the path of the formation of creatine by the cleavage of the endocyclic CN bond of creatinine. The Raman signatures of ring opening are clearly observed after 120 min at pH 8, and further increasing the pH increases the reaction rate even more, as the signatures are observed after 60 and 30 min at pH 10 and 12, respectively; however, the reversibility of the reaction is more prominent at higher pH. Therefore, pH 8 is the most favorable among the three pH values for the decyclization reaction to be stable at room temperature. The proper understanding of this reaction where a toxic substance is converted to a beneficial compound is expected to open the scope for further extensive research.

Temperature dependent polymorphism of pyrazinamide: An in situ Raman and DFT study

The α and γ polymorphs of drug pyrazinamide have been detected with the help of temperature dependent Raman spectroscopic technique. Pyrazinamide is a very useful drug used for the treatment of tuberculosis (TB) and plays a significant role in destroying the dormant tubercle bacilli which are not destroyed by other common TB drugs. Temperature dependent Raman spectra suggest polymorphic phase change from α→γ form of pyrazinamide between 145 and 146°C. In situ Raman spectra of pyrazinamide between 145 and 146°C show the conversion of α→γ form by the shift in CO stretching vibration accompanied by several other changes. The phase change is characterized by the breaking of two linear NH⋯O type hydrogen bonds associated with CO stretching vibration in α dimer and formation of one linear NH⋯N type hydrogen bond along with a weak intramolecular CH⋯O type hydrogen bond in the γ dimer.

Monitoring the In Vitro Thiazolidine Ring Formation of Antioxidant Drug N-Acetyl-L-Cysteine at Basic pH and Detection of Reaction Intermediates: A Raman Spectroscopic and Ab Initio Study

The important cyclization reaction of antioxidant drug N-acetyl-l-cysteine (NAC) has been monitored in vitro at basic pH with the help of time series Raman spectroscopy. The thiazoline ring formation of NAC at acidic pH is a well-known reaction and has been studied extensively. However, the formation of a thiazolidine ring from NAC at basic pH has not been investigated precisely till date. The effect of basicity of the medium on the rate of cyclization has been investigated by studying the reaction at five different basic pH values. Raman signatures of cyclization have been observed with the passage of time and are found to appear faster as the basicity of the medium increases. Ab initio calculations have been done to understand the plausible mechanism of the reaction at basic pH. It is observed that formation of a thiazolidine ring from NAC occurs primarily in four steps, which involve proton abstraction from the thiol (SH) group of NAC and subsequent formation of an S-C bond by a nucleophilic attack of the C-S group on the protonated C-O-H group in NAC. Correlation of the theoretically calculated results with experimental Raman spectral analysis has led to a detailed and proper understanding of this important biochemical reaction.

Structural and Magnetic Studies of Thermally Treated NiFe2O4 Nanoparticles

The heat treatment of nanoparticles can have a direct effect on their particle sizes, which, in turn, can influence many of their structural and magnetic properties. Here, we report the effect of sintering temperature on the chemically synthesized high-quality NiFe2O4 nanoparticles. The structural studies show the formation of pure NiFe2O4 nanoparticles with the space group