Biomedical subjects

P Ramamurthy

Publications and source records attributed to P Ramamurthy.

7 recordsLinked to original sources

PubMed2006

PET suppression of acridinedione dyes by urea derivatives in water and methanol.

Spectroscopic investigations involving the interaction of acridinedione dyes with urea and its derivatives in water and methanol were carried out by absorption, steady-state fluorescence, and time-resolved fluorescence measurements. The hydrogen-bonding properties of urea and derivatives in aqueous solutions are found to be distinctly different from those observed in methanol. Urea, which can serve both as a hydrogen bond donor as well as an acceptor and has a unique hydrogen-bonding feature, helps in studying urea interaction with fluorophores in aqueous solutions, micelles, and alcohol. In our studies, we have used acridinedione dyes as the probe. We report that the hydrophobic interaction of urea with dye predominates by weakening of the hydrogen-bonding interaction of the solvent and urea derivatives with increase in the hydrophobicity of urea derivatives. In methanol, the hydrogen bonding between solvent and urea derivatives predominating over the hydrophobicity of the urea derivatives is observed. The presence of alkyl group substitution in the N-H moiety with a function of increasing concentration resulting in the creation of a more favorable hydrophobic environment to the dye molecule to reside in the hydrophobic shell phase rather than in the bulk aqueous phase is illustrated. The hydrophobic interaction of dye with urea in aqueous solution predominates because of the weakening of the hydrogen bonding of the solvent and urea derivatives, and the photoinduced electron transfer (PET) process is used as a marker to identify the hydrophobic interaction illustrated in our studies.

Acridines↗

PubMed2006

Anomalous association and fluorophore influence on the position of dimethylaniline in micelles: fluorescence quenching of 1,8-acridinedione.

Fluorescence quenching of 9,10-dimethyl-3, 4,6,7,9,10-hexahydro-1,8(2H,5H) acridinedione (ADD) dye by N,N-dimethylaniline (DMA) in SDS and CTAB were studied by steady state fluorescence and time resolved techniques. The Stern-Volmer plots for the quenching of ADD by DMA is found to be linear and the Stern-Volmer constant K(SV) depends on the micellar concentration. The fluorescence quenching analysis reveals the binding of DMA with the micelles. The perturbation of the probe on the position of DMA molecule in micelle is inferred in the present investigation. The ADD fluorophore drives the DMA molecule into the non-polar region (core) of the micelle whereas other fluorophores like pyrene and rhodamine6G do not affect the position of DMA. In this report, the importance of the nature of fluorophores in determining the position and association of the quencher molecules in the aggregated systems is being discussed.

Acridines↗

PubMed2002

Solvent effects and photophysical studies of a new class of acridine(1,8)dione dyes.

Spectroscopic properties of a new family of acridinedione dyes are reported. The absorption and fluorescence spectra of the different substituted acridinediones have been recorded in different solvents and the difference in the dipole moment between ground and excited state has been obtained by solvatochromic shift method. The value of the Onsager cavity radius was calculated from the total surface area using software PCMODEL. Fluorescence quantum yield and fluorescence lifetime were determined. Radiative and non-radiative constants have been calculated. The triplet-triplet absorption maxima and triplet lifetime show variation depending on the substitution.

Acetonitriles↗

PubMed2002

Spectral and photophysical properties of 1,6-naphthyridine derivatives: a new class of compounds for nonlinear optics.

1,6-Naphthyridines are a class of compounds that exhibit second harmonic generation on excitation with a Nd-YAG laser (1064 nm). Solvatochromism has been used to estimate enhancement in the dipole moments on excitation and the values of first-order hyperpolarizability, beta. Photophysical studies on the title compounds show that they have a fluorescence lifetime of about 10 ns and fluorescence quantum yield of approximately 0.05-0.1 in different solvents. Kurtz powder method has been used to find the NLO efficiency of the compounds with reference to urea.

Chemical Phenomena↗

PubMed1996

Recombinant decorin glycoforms. Purification and structure.

The vaccinia virus/T7 bacteriophage expression system was used to express human decorin in HT-1080 cells by co-infection with vTF7-3, encoding T7 RNA polymerase, and vDCN1, encoding the decorin core protein fused to a polyhistidine-insulin signal sequence fusion-protein cassette. Overexpression using the vaccinia virus/T7 phage system resulted in secretion of approximately 30 mg of decorin/10(9) cells per 24 h which enabled purification and separation of multiple glycoforms under native conditions. Cells were cultured in the presence of [35S]methionine or a mixture of [3H]glucosamine and [35S]sulfate, and recombinant glycoprotein purified by metal affinity chromatography which resolved the secreted decorin into two classes, a proteoglycan form and a core protein form. About 25% of the recombinant protein was secreted into the culture medium as core protein devoid of glycosaminoglycan chains. The decorin core protein was resolved into two forms (approximately 49 and approximately 53 kDa) that differed in the extent of N-linked oligosaccharide substitution (2 and 3 N-linked oligosaccharides, respectively). Deglycosylation of the recombinant proteoglycans and core proteins resulted in a single band migrating with an apparent molecular mass approximately 43 kDa when analyzed by SDS-polyacrylamide gel electrophoresis. Far-UV circular dichroism spectra of native decorin proteoglycan showed a minima at 218 nm, consistent with a secondary structure that is predominantly beta-sheet. Circular dichroism spectra of bovine decorin extracted from articular cartilage and recombinant decorin similarly treated revealed a minima of 205 nm indicating a loss of secondary structure. The affinity of decorin proteoglycan and core protein for collagen-like molecules was demonstrated, with the complement component C1q exhibiting the most striking affinity for decorin, although adherence to collagen types I and V was also observed. The extensive secondary structure maintained in the purified recombinant protein is likely to be important for the biological function of decorin.

Animals↗

PubMed1996

Eukaryotic expression of recombinant biglycan. Post-translational processing and the importance of secondary structure for biological activity.

Biglycan is a small chondroitin sulfate proteoglycan found in many tissues and is structurally related to decorin, fibromodulin, and lumican. The biological function of biglycan is poorly understood, although several studies have indicated interaction with other extracellular matrix components. We have initiated studies of structural and functional domains of biglycan by transient eukaryotic expression using the vaccinia virus/T7 bacteriophage expression system. A recombinant vaccinia virus, vBGN4 encoding the mature biglycan core protein as a polyhistidine fusion protein under control of the T7 phage promoter was expressed in HT-1080 cells and UMR106 cells. The structure of the recombinant biglycan secreted by these cells was defined by analyzing molecules labeled in the presence of [35S]sulfate, [3H]glucosamine, and [35S]methionine. Glycoforms of biglycan were separated by imidazole gradient elution, under non-denaturing conditions, and comprised: a large proteoglycan form substituted with two chondroitin sulfate chains of molecular mass approximately 34 kDa (HT-1080 cells) or approximately 40 kDa (UMR106 cells); a small proteoglycan form substituted with two chondroitin sulfate chains with a median molecular mass approximately 28 kDa; and a core protein form secreted devoid of glycosaminoglycan chains. All the glycoforms were substituted with two N-linked oligosaccharides, and the disaccharide composition of the two glycosaminoglycan populations were identical. Approximately 70% of the recombinant biglycan secreted by HT-1080 cells was substituted with chondroitin sulfate chains, whereas about 50% of the biglycan expressed by UMR106 cells was substituted with chondroitin sulfate chains. Infection with vBGN4 in both HT-1080 and UMR106 cells resulted in the production of approximately 10 mg of biglycan/10(9) cells per 24 h. The native recombinant biglycan was shown to bind to collagen type V and the complement protein, C1q. However, when the secondary structure of recombinant biglycan was disrupted by exposure to 4 M guanidine hydrochloride, the affinity for collagen type V was dramatically reduced. These data demonstrate the importance of secondary structure to the function of this small proteoglycan.

Amino Acid Sequence↗

PubMed1996

Transcription, translation, and cellular localization of three Autographa californica nuclear polyhedrosis virus structural proteins: ODV-E18, ODV-E35, and ODV-EC27.

This paper identifies two structural proteins of the occluded derived viral envelope of Autographa californica nuclear polyhedrosis virus (AcMNPV): ODV-E18 and ODV-E35. In addition, we identify a protein, ODV-EC27, that is incorporated into the capsid of occluded virus, which is not detected in budded virus. The genes for these proteins reside within the IE0 intron. The intron was sequenced, and five open reading frames (ORF) were identified. ORF 3 (genomic ORF 143) codes for the ODV envelope protein, ODV-E18. ORF 4 (genomic ORF 144) codes for ODV-EC27, and Western blot analyses locate this protein to both the ODV capsid and envelope. Transcripts for both ODV-E18 and ODV-EC27 initiate from conserved TAAG motifs, and transcripts are detected from 16 through 72 hr p.i. Antiserum to ODV-E18 recognizes a band of 18 kDa on Western blots of extracts from infected cells and bands of 18 and 35 kDa on Western blots of proteins from purified ODV envelope. N-terminal amino acid sequencing reveals that both ODV-E18 and ODV-E35 contain the same N-terminus. Antiserum to ODV-EC27 recognizes a protein of 27 kDa on Western blots of extracts from infected cells and bands of 27 and 35 kDa on Western blots of proteins from purified ODV. Using immunogold labeling techniques, ODV-E18 and/or ODV-E35 are detected in viral induced intranuclear microvesicles and are not detected in the plasma membrane, cytoplasmic membranes, or the nuclear envelope. Immunogold labeling using antisera to ODV-EC27 detects this protein on both the ODV envelope and capsid.

Amino Acid Sequence↗