Biomedical subjects

T Ramasami

Publications and source records attributed to T Ramasami.

At least 19 recordsLinked to original sources

PubMed2006

Role of aspartic acid in collagen structure and stability: A molecular dynamics investigation.

A molecular dynamics (MD) simulation study has been carried out to understand the stability of the triple helical collagen models. The calculations show that the presence of the aspartic acid residue in different positions leads to the local variation in the structure. Analyses of root-mean-square deviation (RMSD), radial distribution function (RDF), puckering effect, dihedral angle variation, hydrogen bond (H-bond), and conformational changes during molecular dynamics simulation reveal that the local perturbation in the sequences, increase in chain flexibility due to removal of five membered rings in the collagen by aspartic acid, change of intermolecular H-bonding pattern, and differences in the association of water are mainly influencing the nature of stabilization of collagen by aspartic acid.

Amino Acid Sequence↗

PubMed2006

Biodegradability of leathers through anaerobic pathway.

Leather processing generates huge amounts of both solid and liquid wastes. The management of solid wastes, especially tanned leather waste, is a challenging problem faced by tanners. Hence, studies on biodegradability of leather become imperative. In this present work, biodegradability of untanned, chrome tanned and vegetable tanned leather under anaerobic conditions has been addressed. Two different sources of anaerobes have been used for this purpose. The effect of detanning as a pretreatment method before subjecting the leather to biodegradation has also been studied. It has been found that vegetable tanned leather leads to more gas production than chrome tanned leather. Mixed anaerobic isolates when employed as an inoculum are able to degrade the soluble organics of vegetable tanned material and thus exhibit an increased level of gas production during the initial days, compared to the results of the treatments that received the anaerobic sludge. With chrome tanned materials, there was not much change in the volume of the gas produced from the two different sources. It has been found that detanning tends to improve the biodegradability of both types of leathers.

Anaerobiosis↗

PubMed2006

Structural influence of mono and polyhydric alcohols on the stabilization of collagen.

In the present study, solvents effects on the structure of collagen have been examined by circular dichroism and their interfacial tension at glass/liquid and Teflon/liquid. Changes in the conformations of the protein have been analyzed after equilibration with aqueous solutions of monohydric and polyhydric alcohols like methanol, ethanol, n-propanol, propane-2-diol and glycerol. The results from viscosity and Circular dichroism (CD) spectra suggest a clear distinction in the structural changes for collagen with monohydric alcohols as against polyhydric ones. The surface tension and interfacial tension at glass (high surface energy, HFSE) and Teflon (Low surface energy, LSFE) reflect similar differences between the monohydric and polyhydric alcohols. Studies on the interfacial energy of the adsorbed protein at glass/solution interface compared to that of Teflon/solution interface show that the water structure near glass gets perturbed leading to an increase in the average free energy of the bulk water phase and a reduction in hydrophobic effect near the glass. The results suggest that the different solvents alter the hydrophobic effect on the hydrated protein to different extent and thus influence folding equilibrium of the protein without directly interacting with it. Polyhydric alcohols seem to favor the native collagen structure while monohydric alcohols enhance it.

Acetates↗

PubMed2005

Stabilization of collagen using plant polyphenol: role of catechin.

Collagen, a unique connective tissue protein finds extensive application as biocompatible biomaterial in wound healing, as drug carriers, cosmetics, etc. A work has been undertaken to study the stabilization of type I collagen using the plant polyphenol catechin. Catechin treated collagen fibres showed a shrinkage temperature around 70 degrees C implying that catechin is able to impart thermal stability to collagen. Catechin treated collagen fibres has been found to be stable even after treatment with high concentration of the secondary structural destabilizer, urea. Circular dichroism studies revealed that there is no major alteration in the structure of collagen on treatment with catechin. The study has demonstrated the involvement of hydrogen bonding and hydrophobic interactions as the major forces involved in the stabilization of collagen by the plant polyphenol, catechin.

Animals↗

PubMed2005

Structure and conformation of intramolecularly cross-linked collagen.

This work reports the effects of cross-linking agent like formaldehyde (HCHO) and glutaraldehyde (GA) on monomeric collagen and its conformational stability using circular dichroism. The nature of the bonds formed and the stability of the cross-links introduced vary with the aldehyde. The amount of HCHO required is four times greater than GA to induce similar changes in the molar ellipticity. This is due to the structural changes of collagen-aldehyde reaction. The change in the molar ellipticity and Rpn ratio for HCHO and GA treated collagen suggest possible aggregation of collagen molecule. The relative viscosity of native and aldehyde treated collagen was measured and correlated to the changes seen in the CD spectra. The small amount of aldehydes are needed to induce changes in the conformational stability of collagen. This can be applied to the biomaterial and biomedical application.

Animals↗

PubMed2005

Value added eco-friendly products from tannery solid wastes.

Chrome shavings are the prominent solid wastes in tanning industry. Since chromium is known for its toxicity, the disposal of chrome shavings has been identified as a serious problem from the environmental point of view. At present, the popular utilization mode for chrome shavings is the manufacture of leather boards and related products. But this does not offer complete utilization of chrome shavings. Moreover, return per ton of chrome shavings is low if used for leather board production. In view of this, two processes have been developed to offer an alternative and better solution for the disposal of chrome shavings. The first process is preparation of parchment like membrane and the second process is related to development of leather like material. These products are analyzed for their mechanical behavior and other physicochemical properties. Parchment membrane can be used in the preparation of lampshades, chandeliers, wall hangers, table tops etc. and leather like material can be used in the preparation of chappal uppers, hand bags, purses, valets etc. The utilization of the chrome shavings in preparation of those two products not only reduces the environmental pollution but at the same time value added products can also be obtained.

Chromium Compounds↗

PubMed2002

Biophysical behavior of Scomberoides commersonianus skin collagen.

Some biophysical characteristics of the skin collagen from Scomberoides commersonianus were measured and compared to those of rat tail tendon. Stress-strain data indicate that the strain at break as well as the tensile strength of the fish skin without scales increased significantly. The maximum tension in case of rat skin is at least a factor of two higher than that observed in fish skin. The much lower hydrothermal isometric tension measurements observed in fish skin are attributable to a lesser number of heat stable crosslinks. Stress relaxation measurements in the fish skin indicate that more than one relaxation process may be involved in the stabilization of collagenous matrix. The observed differences in the biophysical behavior of fish skin may well arise from combination of changes in extent of hydroxylation of proline in collagen synthesis, hydrogen bond network and fibril orientation as compared to rat tail tendon.

Animals↗

PubMed2001

Apoptosis of lymphocytes in the presence of Cr(V) complexes: role in Cr(VI)-induced toxicity.

Cr(VI) compounds have been declared as a potent occupational carcinogen by IARC (1990) through epidemiological studies among workers in chrome plating, stainless-steel, and pigment industries. Studies relating to the role of intermediate oxidation states such as Cr(V) and Cr(IV) in Cr(VI)-induced carcinogenicity are gaining importance. In this study, issues relating to toxicity elicited by Cr(V) have been addressed and comparisons made with those relating to Cr(VI) employing human peripheral blood lymphocytes. Lymphocytes have been isolated from heparinized blood by Ficoll-Hypaque density gradient centrifugation and exposed to Cr(V) complexes viz. sodium bis(2-ethyl-2-hydroxybutyrato)oxochromate(V), Na[Cr(V)O(ehba)(2)], 1 and sodium bis(2-hydroxy-2-methylbutyrato)oxochromate(V), Na[Cr(V)O(hmba)(2)], 2 and Cr(VI). The phytohemagglutinin (PHA)-induced proliferation of lymphocytes has been found to be inhibited by the two complexes of Cr(V) and chromate Cr(VI) in a time- and concentration-dependent manner. Viability of cells decreases in the presence of Cr(V). Apoptosis appears to be the mode of cell death in the presence of both Cr(V) and Cr(VI). Pretreatment of cells with antioxidants before exposure to chromium(V) complexes reverse apoptosis partially. Possibility for the formation and implication of reactive oxygen species in Cr(V)-induced apoptosis of human lymphocyte cells has been indicated in this investigation. The intermediates of Cr(V) and radical species in the biotoxic pathways elicited by Cr(VI) seems feasible.

Antioxidants↗

PubMed2001

Chromium(III)-induced structural changes and self-assembly of collagen.

Rat tail tendon (RTT) collagen has been reacted with a homologous series of chromium(III) complexes viz., (H2O)(4)Cr(OH)(2)Cr(H2O)(4+)(4) 1 (dimer), Cr(3)(OH)(4)(H2O)(5+)(9) 2 (trimer), and Cr(4)(OH)(4)(O2)(H2O)(4+)(12) 3 (tetramer), and the structural alterations brought about by these complexes have been investigated through atomic force microscopy (AFM) and circular dichroism (CD) studies. Examination of Cr(III)-treated tendons using AFM revealed changes in the D-periodicity of collagen, which may arise due to differences in the topological distribution of various Cr(III) complexes. Evidence for organisation of monomeric collagen into quarter staggered fibrils in the presence of Cr(III) dimer, 1, has been obtained. The quaternary structural changes induced by chromium in the protein have been correlated to the conformational changes of collagen in the absence of denaturation.

Acetic Acid↗

PubMed2001

Speciation and recovery of chromium from chromite ore processing residues.

The processing of chromite ore is associated with the generation of large quantities of solid wastes containing chromium, which have been disposed of as landfill for many years. The mobilization and operational speciation of chromium contained in soils contaminated with metal salts are important in terms of the environment. Several methods have been employed for the extraction and recovery of solid wastes. Chromium contained in contaminated soils and solid wastes can be categorized as exchangeable, oxidizable, carbonate-bound, reducible and residual. The results from this study indicate a need for efficient leaching methodologies in chromite ore processing plants to decrease the non-detrital fractions of chromium in the residue. Aggressive methodologies are required to recover chromium from the detrital fractions. The potential benefits of employing sodium peroxide for the complete recovery of chromium from chromite residue have been demonstrated, and the need to ensure the safety of the process has been emphasized.

Chromium↗

PubMed2000

Inhibition of collagenase by Cr(III): its relevance to stabilization of collagen.

Bacterial collagenase has now been reacted with a select series of Cr(III) complexes and modifications in the activity of chromium-modified collagenase has been deduced from the extent of hydrolysis of (2-furanacryloyl-L-leucyl-glycyl-L-prolyl-L-alanine), FALGPA. A homologous series of Cr(III) complexes with dimeric, trimeric and tetrameric structures as in 1, 2 and 3 respectively has been investigated for their ability to inhibit the action of collagenase against FALGPA. Whereas competitive and non-competitive modes of inhibition of collagenase are expressed by 1, (dimer) and 2, (trimer) respectively, the tetramer, 3, exhibits poor affinity to collagenase and the inhibition of the enzyme activity is uncompetitive. Evidence for different modes of inhibition of collagenase depending on the nature of Cr(III) species has been presented in this work. Circular dichroism and gel electrophoresis data on Cr(III) modified collagenase corroborate the hypothesis that the inhibition of collagenase by the heavy metal ion arises from secondary and quaternary structural changes in the enzyme. The implications of the observed Cr(III) species specific inhibition of collagenase in gaining new insight into the mechanism of stabilization of collagen by Cr(III) are discussed.

Cations↗

PubMed2000

Stabilization of chromium(V) species in bovine serum albumin adduct.

A detailed investigation of molecular interactions of the protein bovine serum albumin (BSA) with potassium dichromate has been made. Compelling evidence for the formation of a relatively stable Cr(V) species which decays only slowly to afford Cr(III) products has been obtained. The resulting final chromium(III) product mediates in cross-linking of BSA. The implications of the formation of a relatively stable chromium(V) as well as chromium(III)-mediated cross-links in the marker protein are discussed in the context of the metal ion-induced biotoxicity.

Animals↗

PubMed2000

A novel and single step ultrastructural method for staining biological tissues embedded in common embedding media.

A new single step staining method is described which is very simple, rapid and reproducible with better contrast than the widely employed uranyl acetate-lead citrate double staining method for observation of cell organelles in various tissue sections using transmission electron microscope. A copper uranyl acetate solution was employed to stain the ultrathin sections of tissues embedded in either water-miscible or water-immiscible resin media. The staining results are excellent. Cell organelles and extracellular matrix are stained with no artifactual precipitation or granulation.

Animals↗

PubMed1999

Chromium(III) hydrolytic oligomers: their relevance to protein binding.

The nature of chromium(III) complexes has been found to show a profound influence in its interaction with collagen. The hydrothermal stability of rat tail tendon (RTT) fibres treated with dimeric, trimeric and tetrameric species of chromium(III) has been found to be 102, 87 and 68 degrees C, while that of native RTT is 62 degrees C. This shows that the efficiency of crosslinking of collagen by chromium(III) species is dimeric > trimeric > tetrameric. This order of stabilisation is again confirmed by cyanogen bromide (CNBr) cleavage of RTT collagen treated with dimeric, trimeric and tetrameric chromium(III) species. CNBr has been found to cleave the collagen treated with tetrameric chromium(III) species extensively. On the other hand, dimer-treated collagen does not undergo any cleavage on CNBr treatment. The equilibrium constants for the reaction of a nucleophile like NCS(-) to the dimeric, trimeric and tetrameric species of chromium(III) have been found to be 15.7+/-0.1, 14.6+/-0.1 and 1.2+/-0.1 M(-1), respectively. These equilibrium constant values reflect the relative thermodynamic stability of the chromium(III) species-nucleophile complex. The low stabilising effect of the tetrameric species can be traced to its low thermodynamic affinity for nucleophiles.

Animals↗

PubMed1999

Hydroxopentaamminechromium(III) promoted phosphorylation of bovine serum albumin: its potential implications in understanding biotoxicity of chromium.

Evidence for chromium(III) induced phosphorylation of a biomarker protein bovine serum albumin (BSA) is presented. Radiolabelled adenosine 5'-triphosphate (ATP) was reacted with BSA in the presence of various Cr(III) salts. While [Cr(NH3)5(H2O)]3+ brought about phosphorylation of BSA, several Cr(III) complexes, viz. [Cr(bpy)3]3+, [Cr(phen)3]3+, [Cr(en)3]3+, [Cr(salen)(H2O)2]+ and [Cr(salprn)(H2O)2]+, did not phosphorylate BSA. The Cr(III) mediated the transfer of gamma- and alpha-phosphates but not the adenine and the sugar moieties of the ATP molecule to BSA. The observed stoichiometry was 0.75 mol Pi to mol BSA for the gamma-phosphate and 0.5 mol Pi to mol BSA for the alpha-phosphate of ATP. The presence of serine phosphate and threonine phosphate was detected in the hydrolysate of phosphorylated BSA by means of comparison of Rf values with authentic samples of phosphoserine and phosphothreonine after chromatographic separation and autoradiography. [Cr(NH3)5(H2O)]3+ at pH 7.4 is known to exist as the conjugate base [Cr(NH3)5(OH)]2+ and is capable of ligand substitution involving metal-oxygen bond retention. Such anation reaction of [Cr(NH3)5(OH)]2+ with ATP subsequently leads to the esterification of alcoholic hydroxyl groups of serine and threonine of BSA. Possible consequences of chromium(III) induced in vivo phosphorylation of proteins are discussed.

Adenosine Triphosphate↗

PubMed1998

Phase Transition in Langmuir Films of Octadecylmalonic Acid.

The phase transitions observed in the surface pressure-molecular area (pi-A) isotherms of monolayers of the dicarboxylic compound octadecylmalonic acid (OMA) at the air/water interface were investigated using molecular dynamics simulation in the molecular area ranging from 20 to 50 A2/molecule in a triangular lattice. Potential energy, torsion angles, and hydration of the head groups under periodic boundary conditions have been used for the study. Hydration was done by a stacked array of water molecules relaxing under these boundary conditions. Twelve simulations were performed at T = 300 K to study the conformation of the packed molecular system. Bonded and nonbonded interaction potentials were taken from Biosym force fields. The transitions seen in the pi-A curves are explained from the breaks in the plots of potential energy at various concentrations, related to a liquid expanded-to-liquid condensed (LE/LC) transition, and classified under the first order type. Electron diffraction patterns of these films transferred onto transmission electron microscopy (TEM) grids were studied by high-resolution imaging and showed a clear transition from the LE to the LC phase. Copyright 1998 Academic Press.

Journal Article↗

PubMed1995

Chromium(III) induced abnormalities in human lymphocyte cell proliferation: evidence for apoptosis.

The occupational hazards and respiratory problems of workers associated with the chromium related industries like mining, electroplating and tanning have received much focus. Although the cytotoxic and mutagenic effects of common chromium(VI) compounds are now established, to the best of our knowledge, this is the first report of apoptosis (programmed cell death) caused by a set of Cr(III) complexes in human lymphocyte cells. The effects of five Cr(III) complexes with differing ligand environment and structure as well as K2Cr2O7 on Phytohaemagglutinin (PHA) induced lymphocyte cell proliferation have been investigated. Two of the Cr(III) complexes and K2Cr2O7 are found to cause apoptosis of lymphocytes but not the others. A case for the importance of species specific effects rather than non specific metal oxidation state dependent processes has now been made.

Apoptosis↗

PubMed1989

Chymotrypsin-catalyzed hydrolysis of chromium (III) derivatives of insulin: evidence for stabilization of the protein through interactions with metal ions.

We investigated the chymotrypsin-promoted hydrolysis of a series of chromium(III)-insulin complexes containing chelating or macrocyclic ligands. It has been shown that Cr(III) stabilizes insulin against the chymotrypsin-promoted hydrolysis of the protein. The molecular weights of Cr(III) containing peptides have been estimated to be of the order of 2,700-3,700 daltons. The Cr(III) containing peptides are richer in glutamic acid than the intact insulin and are devoid of any isoleucine. High molecular weights and the observed glutamic acid/histidine ratios in Cr(III) containing peptides have been rationalized in terms of Cr(III) being associated with insulin aggregates rather than the monomer of the protein. The chymotrypsin hydrolysis of Cr(III) insulin derivatives is influenced markedly by the nature, charge, and type of Cr(III) complex with which the protein has been reacted. Arguments have been advanced that chymotrypsin-promoted hydrolysis of insulin Cr(III) derivatives does not lead to cleavages at or near every tyrosine residue.

Chromium↗