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Biomedical subjects

K Bhattacharyya

Publications and source records attributed to K Bhattacharyya.

At least 19 recordsLinked to original sources
PubMed2001

Pseudokobusine.

The title compound, hetisan-6,11beta,15beta-triol, C20H27NO3, is a hetisane-type diterpenoid alkaloid. It consists of six six-membered rings and two five-membered rings. The fused-ring system contains three chair, two boat, one distorted boat and two envelope conformations. Intramolecular and intermolecular hydrogen bonds are present between the O atoms, with O...O separations of 3.006 (3) and 2.743 (3) A, as well as an O...N intermolecular interaction of 2.887 (3) A.

Bridged-Ring Compounds↗
PubMed2000

(24R)-24,25-Dihydroxycycloartan-3-one.

In the title compound, C(30)H(50)O(3), the three six-membered rings adopt chair, twist and twist-boat conformations. The five-membered ring is in a slightly distorted envelope conformation. The substituent on the five-membered ring is in an extended conformation, with its two hydroxyl O atoms forming an intramolecular hydrogen bond. One of these O atoms also forms an intermolecular hydrogen bond with the oxygen of the carbonyl group in a neighbouring molecule.

Crystallography, X-Ray↗
PubMed1998

A fluorescence spectroscopic and molecular dynamics study of bis-ANS/protein interaction.

Despite emergence of bis-ANS as a major fluorescence probe of proteins structure, conformational and spectroscopic properties of protein/bis-ANS complexes remains largely unexplored. We have shown that fluorescence polarization of both ANS and bis-ANS is excitation wavelength dependent and this is a property of all protein-ANS/bis-ANS complexes studied. Bis-ANS excitation maximum is always more red shifted than the corresponding ANS complex. Even when corrected for the red shift, the bis-ANS complexes in some, but not all, cases show only a little lowering of polarization, suggesting modest additional depolarization in bis-ANS compared to ANS. Calculation of energy migration rate between the two rings suggests that energy migration rate should be high at all values of the naphthyl-naphthyl dihedral angle. Although, Molecular mechanics and dynamics calculations show that the lowest energy conformation of bis-ANS is when the two naphthalene rings are roughly perpendicular to each other, due to rapid energy migration this conformation should lead to dramatic lowering of emission anisotropy, unlike what is observed. Salt and temperature dependence of bis-ANS/protein interaction suggests little ionic interaction and pre-dominant interaction through hydrophobic aromatic rings. We conclude that bis-ANS binds to proteins through interaction with the aromatic rings and with two rings nearly parallel to each other.

Amino Acyl-tRNA Synthetases↗
PubMed1996

The use of theory based semistructured elicitation questionnaires: formative research for CDC's Prevention Marketing Initiative.

Through one of its many HIV prevention programs, the Prevention Marketing Initiative, the Centers for Disease Control and Prevention promotes a multifaceted strategy for preventing the sexual transmission of HIV/AIDS among people less than 25 years of age. The Prevention Marketing Initiative is an application of marketing and consumer-oriented technologies that rely heavily on behavioral research and behavior change theories to bring the behavioral and social sciences to bear on practical program planning decisions. One objective of the Prevention Marketing Initiative is to encourage consistent and correct condom use among sexually active young adults. Qualitative formative research is being conducted in several segments of the population of heterosexually active, unmarried young adults between 18 and 25 using a semistructured elicitation procedure to identify and understand underlying behavioral determinants of consistent condom use. The purpose of this paper is to illustrate the use of this type of qualitative research methodology in designing effective theory-based behavior change interventions. Issues of research design and data collection and analysis are discussed. To illustrate the methodology, results of content analyses of selected responses to open-ended questions on consistent condom use are presented by gender (male, female), ethnic group (white, African American), and consistency of condom use (always, sometimes). This type of formative research can be applied immediately to designing programs and is invaluable for valid and relevant larger-scale quantitative research.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Somatostatin in a water-restricted environment: fluorescence and circular dichroism study in AOT reverse micelles.

Steady-state and time-resolved fluorescence emission from the single tryptophan residue of somatostatin, and the kinetics of quenching of this emission, were studied in aqueous solution and in reverse micelles of sodium bis (2-ethylhexyl) sulfosuccinate (AOT)/water/isooctane, a system that mimics the water-membrane interface well. Incorporation into micelles caused blue shifts and reduced band-widths of the emission peaks and altered the quantum yields with respect to emission from bulk water. Steady-state anisotropy values also increased considerably on micellization. These observations point to reduced polarity of the environment around the Trp residue of the peptide, as well as restricted freedom of its rotational motions, due to transfer from the aqueous to the micellar phase. Fluorescence emission kinetics of the Trp moiety followed biexponential decay laws in both aqueous and micellar media. Static and dynamic quenching constants were measured for acrylamide and CCI4 quenchers localized in the micellar and organic pseudophases, respectively, using both steady-state and time-resolved experiments. The efficiency of dynamic quenching by acrylamide became vanishingly small in going from water to reverse micelles, in sharp contrast to the comparable quenching efficiencies exhibited by CCI4 in micelles and acrylamide in water. The circular dichroic (CD) spectrum of the native peptide in water indicated the possibility of some amount of beta-type secondary structure being present. Conformational analysis of CD spectra in micelles showed that the relative amount of this structural feature was enhanced for the micellized peptide but was insensitive to the water content of micelles.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

The household production of health: integrating social science perspectives on micro-level health determinants.

Efforts to control disease and improve health in developing countries require increasing collaboration between social and medical scientists. This collaboration should extend from the early stages of technology development to the evaluation and improvement of population-wide interventions. This paper provides an integrating framework for social science research on health producing processes at the household level, drawing on recent work in economics, anthropology, and public health. Further development of theory and methods in this area would benefit from interdisciplinary research in categories as defined by social and behavioral science in addition to those related to specific diseases and intervention programs.

Breast Feeding↗
PubMed1994

The Marathi "taskonomy" of respiratory illnesses in children.

The reduction of childhood mortality from respiratory infections depends upon a case management strategy which encourages the decision to seek treatment. The research discussed, conducted in Pachod, Maharashtra, India, uses a "taskonomic" approach to understanding the diagnosis of illness and treatment decisions. This approach views treatment decisions as a result not only of local conceptual models of illness, but also of the specific circumstances of illness episodes involving different types of social relationships and control over resources.

Acute Disease↗
PubMed1993

Fluorescence study of melanocyte stimulating hormones in AOT reverse micelles.

Fluorescence emission from the single tryptophan residues of two melanocyte stimulating hormones, alpha-MSH and delta-MSH, and their quenching kinetics were studied in aqueous solution and in reverse micelles of AOT/water/isooctane. Incorporation into micelles caused blue shifted and narrower emission peaks, altered quantum yields and considerably enhanced anisotropies for both peptides when compared to emission from bulk water. The variation of emission parameters with micellar water content was interpreted to suggest that while the tryptophan in alpha-MSH lies in close vicinity of the water-AOT molecular interface, that in delta-MSH is solubilized in the central water pool. Total emission intensity decays followed complex (biexponential) kinetics in both aqueous and micellar media. Although the mean lifetimes for both peptides were always nearly the same, the average rotational correlation times in micelles for alpha-MSH were three times as much as those for delta-MSH. Stern-Volmer plots obtained using acrylamide and CCl4 as quenchers localized in the micellar and organic pseudophases, respectively, were non-linear and dependent on emission wavelength. Quenching by acrylamide was more efficient for delta-MSH than for alpha-MSH, while the opposite was true for quenching by CCl4. The implication of this result for localization of the peptides in micelles was consistent with the earlier one emerging from these studies.

Acrylamides↗