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D Srinivas

Publications and source records attributed to D Srinivas.

15 recordsLinked to original sources
PubMed2006

Synthesis of novel tricyclic oxazolidinones by a tandem SN2 and SNAr reaction: SAR studies on conformationally constrained analogues of Linezolid.

A series of conformationally constrained analogues of Linezolid were synthesised by employing a tandem SN(2) and SNAr reaction as the key step and tested for antibacterial activity. While the hexahydroazolo-quinoxaline compounds were inactive, the tetrahydroazolo-benzothiazine compounds exhibited interesting antibacterial activity. The introduction of fluorine in the aromatic ring further made the compounds more potent in acetamide compounds resulting in an interesting analogue 32. However, the introduction of fluorine (analogue 34) on the already potent non-fluorine thiocarbamate 21 did not have any influence on the activity.

Acetamides↗
PubMed2006

Chemoselective alkane oxidation by superoxo-vanadium(V) in vanadosilicate molecular sieves.

Electron paramagnetic resonance (EPR) spectroscopy of reactive superoxo-vanadium(V) species in vanadosilicate molecular sieves (microporous VS-1 and mesoporous V-MCM-41) generated on contact with H2O2, tert-butyl hydroperoxide (TBHP), or (H2+O2) is reported for the first time. By suitable choice of the silicate structure, solvent, and oxidant, we could control the vanadium-(O2-*) bond (i.e., the V-O bond) covalency, the mode of O-O cleavage (in the superoxo species), and, therefore, chemoselectivity in the oxidation of n-hexane: Oxidation by TBHP over V-MCM-41, for example, yielded 27.2% of (n-hexanol+n-hexanal+n-hexanoic acid), among the highest chemoselectivities for oxidation of the terminal -CH3 in a linear paraffin reported to date. Over these vanadosilicates, oxidation of the primary C-H bond occurs only via a homolytic O-O bond cleavage; the secondary C-H bond oxidations may proceed via both the homo- and heterolytic O-O cleavage mechanisms.

Journal Article↗
PubMed2005

SOM assembly of hydroxynaphthoquinone and its oxime: polymorphic X-ray structures and EPR studies.

Investigation on solvent-induced polymorphism in X-ray structures of 2-hydroxy-1,4-naphthoquinone (Lawsone) 1, is carried out. In protic methanol, 1 crystallizes in monoclinic space group P2(1)/c (1a) comprising of 2D hydrogen bonded network via cyclic dimers. In aprotic solvent such as acetone on the other hand, 1 exhibits orthorhombic space group Pna 2(1) (1b) and emerges with 1D catemeric chain. Solvent-induced topological isomerism of cyclic dimers and helical catemeric chains arising from (i) bifurcated intra- and inter molecular hydrogen bondings viz. O-H...O=C interactions between C(2) hydroxyl and C(1), C(4) carbonyls, (ii) C-H...O interactions viz. C(3)-H...O(1)C(1) have been discussed. A signal for radical in 1 at g = 2.0058 is signatured by EPR spectrum and it's oxime derivative viz. 2-hydroxy-4-naphthoquinone-1-oxime 2, in solid state shows biradical and monoradical formation with aggregation of dimer and monomer due to non-covalent hydrogen bonds. Zero field split parameters for 2 are estimated to be D = 215 G, Ex = 13 G, Ey = 47 G at 298 K. A half field signal at 77 K indicates triplet ground state. Frozen glass EPR of 2 resolves as regioregular dimeric-monomeric species showing hyperfine interactions with 1-oximino nitrogen in dimer A (14N) = 15.5 G].

Acetone↗
PubMed2005

Role of liquid membrane phenomenon in the biological actions of thioridazine.

Role of surface activity in the mechanism of action of thioridazine (THR) has been studied. THR has been shown to generate liquid membrane it self and also in association with the relevant membrane lipids, sphingomyelin and cholesterol in series with a supporting membrane. Transport of relevant biogenic amines e.g. dopamine, nor-adrenaline, adrenaline, serotonin, gamma amino butyric acid (GABA) and glutamic acid and ions viz. sodium, potassium, and calcium has been studied in the presence of liquid membranes generated by THR and THE in association with sphingomyelin-cholesterol. The data on modifications in the permeability of relevant biogenic amines and ions indicate that the liquid membranes generated by THR may contribute to the mechanism of action of THR.

Biogenic Amines↗
PubMed2005

Plasma Proteome Database as a resource for proteomics research.

Plasma is one of the best studied compartments in the human body and serves as an ideal body fluid for the diagnosis of diseases. This report provides a detailed functional annotation of all the plasma proteins identified to date. In all, gene products encoded by 3778 distinct genes were annotated based on proteins previously published in the literature as plasma proteins and the identification of multiple peptides from proteins under HUPO's Plasma Proteome Project. Our analysis revealed that 51% of these genes encoded more than one protein isoform. All single nucleotide polymorphisms involving protein-coding regions were mapped onto the protein sequences. We found a number of examples of isoform-specific subcellular localization as well as tissue expression. This database is an attempt at comprehensive annotation of a complex subproteome and is available on the web at http://www.plasmaproteomedatabase.org.

Amino Acid Motifs↗
PubMed2001

Bromo-boronolactonization of olefins.

Exposure of a variety of mono- and disubstituted ortho-alkenylarylboronic acids to NBS in THF/H(2)O under neutral conditions affords bromo-boronolactones, in some instances, with exceptional regiocontrol. The adducts, analogous to those formed by carboxylic acids, are shown to be useful synthetic intermediates.

Alkenes↗
PubMed2001

Conformational isomerism and weak molecular and magnetic interactions in ternary copper(II) complexes of [Cu(AA)L']ClO4.nH2O, where AA = L-phenylalanine and L-histidine, L' = 1,10-phenanthroline and 2,2-bipyridine, and n = 1 or 1.5: synthesis, single-crystal X-ray structures, and magnetic resonance investigations.

Weak molecular and magnetic exchange interactions in ternary copper(II) complexes, viz., [Cu(L-phe)(phen)(H(2)O)]ClO(4) (1), [Cu(L-phe)(bpy)(H(2)O)]ClO(4) (2), and [Cu(L-his)(bpy)]ClO(4).1.5H(2)O (3), where L-phe = L-phenylalanine, L-his = L-histidine, phen = 1,10-phenanthroline, and bpy = 2,2'-bipyridine, have been investigated. Single-crystal X-ray structures reveal that complex 2 crystallizes in a monoclinic space group P2(1), with unit cell parameters a = 7.422(7) A, b = 11.397(5) A, c = 12.610(2) A, beta = 102.10(5) degrees, V = 1043.0(11) A(3), Z = 2, R = 0.0574, and R(w) = 0.1657. Complex 3 crystallizes in a monoclinic space group C2, with a = 18.834(6) A, b = 10.563(4) A, c = 11.039(3) A, beta = 115.23(2) degrees, V = 1986.6(11) A(3), Z = 4, R = 0.0466, and R(w) = 0.1211. Molecules of 2, in the solid state, are self-assembled via weak intra- and intermolecular pi-pi stacking and H-bonding interactions. Molecules of 3 exhibit intermolecular dimeric association with the Cu.Cu separation being 3.811 A. X-ray structures and (1)H NMR studies reveal conformational isomerism in both solid and liquid states of complexes 1 and 2. The aromatic side chain of L-phe in 1 and 2 adopts either a "folded" (A) or an "extended" (B) conformation. Variable-temperature (1)H NMR and spin lattice relaxation measurements point out interconversion between conformations A and B at temperatures above 323 K. The change in molecular conformation induces a change in the electron density at the site of copper and band gap energy between HOMO and LUMO orbitals. Interestingly, in spite of paramagnetic nature, complexes 1 and 2 are amenable for both EPR and (1)H NMR spectroscopic studies. Single-crystal EPR spectra of 2 in three orthogonal planes are consistent with three-dimensional magnetic behavior. Intramolecular exchange dominates the dipolar interactions. The EPR spectra of 3 correspond to weak magnetic interactions between associated dimeric units. The structural and magnetic resonance investigations together reveal that the weak pi-pi stacking interactions are the electronic pathways for magnetic interactions in 1-3.

2,2'-Dipyridyl↗
PubMed2000

Synthesis, X-ray structure, single-crystal EPR and 1H NMR studies of a distorted square planar Cu(salEen)2(ClO4)2 complex in a novel bilayered architecture: salEen = N,N-diethylethylenesalicylidenamine.

Single-crystal X-ray structure and spectroscopic characterizations of Cu(salEen)2(ClO4)2, are reported; salEen is a Schiff base condensation product of equimolar amounts of salicylaldehyde and N,N-diethylethylenediamine. The complex crystallizes in a triclinic space group P1 with a = 12.055(4) A, b = 10.652(3) A, c = 12.701(3) A, alpha = 90.54(2) degrees, beta = 94.39(2) degrees, gamma = 91.35(3) degrees, and Z = 2. The coordination geometry around Cu(II) ion is tetrahedrally distorted square planar with salEen coordinating as a neutral bidentate ligand through N and O donor atoms (average Cu-N and Cu-O distances are 2.004 and 1.880 A, respectively). The counterion ClO4- makes H-bonding contacts with the neighboring cation moieties and forms a one-dimensional layered arrangement of the molecules. The pendent, N,N-diethylethylenediamine groups of salEen (from the centrosymmetrically related molecules) in adjacent layers interpenetrate, forming novel bilayered architectures, which are further held together by pi-pi stacking interactions. EPR studies on single crystals, in three mutually orthogonal planes, yield a rhombic g tensor (gx = 2.041(1), gy = 2.073(1), and gz = 2.220(1)) consistent with the distorted square planar geometry of the CuN2O2 moiety. The peak-to-peak line width of the EPR signal exhibits a |3 cos2 theta - 1|4/3 variation, attributable to one-dimensional magnetic exchange behavior of the complex. The analysis suggests that both the dipole-dipole and exchange interactions contribute to the line width. Interestingly, the complex is amenable for both EPR and NMR studies at ambient temperatures. The proton NMR signals are narrow in CD3CN solutions and the HOMO correlation spectroscopy (COSY) studies reveal the 1H connectivities. Nuclear spin lattice relaxation time (T1) measurements, using inversion recovery method, indicate that T1 values for all the protons are remarkably long compared to those of other mononuclear Cu(II) complexes.

Journal Article↗
PubMed1990

Utilization of sugars by Lactobacillus acidophilus strains.

Utilization of various carbohydrates viz., glucose, fructose, sucrose, lactose and galactose by Lactobacillus acidophilus strains was investigated in Lactobacillus Selection Broth. Maximum viable counts, acid production and sugar utilization by different test strains were in the order: glucose greater than or equal to fructose greater than sucrose greater than or equal to lactose greater than galactose. The generation time of the tested strains was shorter in glucose medium as compared to sucrose or lactose medium.

Animals↗
PubMed1984

Wirsungorrhagia or hemoductal pancreatitis: report of a case and review of the literature.

An unusual case of gastrointestinal hemorrhage due to rupture of the splenic artery into the pancreatic duct in a patient with chronic pancreatitis is described. The diagnosis was suspected by observing blood coming from the papilla of Vater during duodenoscopy and corroborated by findings seen on splenic arteriography. Previously reported cases are reviewed. An etiology is discussed and a classification suggested. This obscure cause of gastrointestinal bleeding should be suspected when the more common causes of bleeding have been satisfactorily ruled out.

Adult↗
PubMed1983

Toothpick perforation of the duodenum.

An 82-year-old man developed gastrointestinal hemorrhage and polymicrobial sepsis from toothpick perforation of the duodenal bulb. We removed the toothpick endoscopically.

Aged↗
PubMedDate not supplied

Comparison of two systems of classification of leprosy based on number of skin lesions and number of body areas involved--a clinicopathological concordance study.

BACKGROUND AND AIMS: WHO guidelines classify leprosy patients for therapeutic purposes into paucibacillary (PB) and multibacillary (MB) leprosy based on the number of skin lesions. An alternative system of classification has been in practice in Nepal from 1985 onwards, based on the number of body areas involved in patients of leprosy. We attempted a clinicopathological approach for comparison of these two systems of classification in leprosy patients for their ability to demarcate patients into groups of PB and MB leprosy. MATERIALS AND METHODS: The study included 108 leprosy patients (80 males and 28 females). Complete clinical examination and body charting was carried out in each patient noting the count of skin lesions and the number of body areas involved. Slit skin smears and skin biopsies were taken from an active skin lesion in all patients. RESULTS: On analysis, it was observed that there was good clinicopathological correlation between patients with 5 or < 5 skin lesions and 2 or < 2 body areas involved. (Clinical 95% and histological 96%) A similar correlation was also observed in the other group of patients with > 5 skin lesions and > 2 body areas involved, (Clinical 94% and histological 96%). There were almost identical numbers of patients represented in these two groups of classification. CONCLUSIONS: Our findings suggest that patients with involvement of 2 or less body areas can be classified as PB leprosy and those with more than 2 body areas involved can be classified as MB leprosy for the purposes of therapy. The study of areas of involvement in leprosy patients not only provides additional patient information but also adds another parameter as a basis for the study of leprosy patients.

Female↗