R Rajaram

Central Leather Research Institute, Chennai, State of Tamil Nadu, India

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Publications (10)25.56 Total impact

  • Journal- Society of Leather Technologists and Chemists 01/2002; 86(3):106-111. · 0.65 Impact Factor
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    ABSTRACT: 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.
    Biochemical and Biophysical Research Communications 09/2001; 285(5):1354-60. · 2.41 Impact Factor
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    ABSTRACT: 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.
    Biochemical and Biophysical Research Communications 05/2001; 283(1):229-35. · 2.41 Impact Factor
  • R Gayatri, R Rajaram, T Ramasami
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    ABSTRACT: 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.
    Biochimica et Biophysica Acta 01/2001; 1524(2-3):228-37. · 4.66 Impact Factor
  • K M Ananth, R Rajaram, T Ramasami
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    ABSTRACT: 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.
    Biochemical and Biophysical Research Communications 08/2000; 273(3):1138-43. · 2.41 Impact Factor
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    ABSTRACT: 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.
    Biochimica et Biophysica Acta 11/1999; 1472(3):595-602. · 4.66 Impact Factor
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    ABSTRACT: 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.
    Biochimica et Biophysica Acta 06/1999; 1427(3):357-66. · 4.66 Impact Factor
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    ABSTRACT: Mechanistic insight has been gained into the diverse roles played by some chromium(III) ions in biosystems. Experimental evidence to show that chromium may serve to assemble insulin rather than insulin-receptor units has been obtained. A proposal that stabilisation of insulin by Cr(III) may be responsible for the beneficial role of Cr(III) in glucose metabolism has also been made. Although one of the well-known industrial applications of chromium(III) salts has been in the stabilisation of the collagen in skin to produce leather, it has remained difficult to provide a molecular basis to tanning. Results of model studies involving the reactions of collagen with a series of complexes of chromium(III) have been presented and an attempt to provide a molecular basis to the stabilisation of collagen by the metal ion have been made. In view of the growing concern about the ecological consequences as well as the occupational hazards of using chromium, abnormalities induced by a series of chromium complexes on the proliferation of human lymphocytes have been investigated. Evidence for apoptosis by Cr(III) has been obtained. Although chromium plays diverse functional roles in biosystems, a perspective discussion of some common features in the nature of interactions of the metal ion with biomolecules has been attempted.
    Journal of Chemical Sciences 01/1997; 109(5):307-317. · 1.30 Impact Factor
  • R Rajaram, B U Nair, T Ramasami
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    ABSTRACT: 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.
    Biochemical and Biophysical Research Communications 06/1995; 210(2):434-40. · 2.41 Impact Factor
  • A. Rajaram, R. Rajaram
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    ABSTRACT: Calcium apatite powder was formed and a definite quantity was mixed separately with 1% solutions of gelatin, chitosan and collagen to form a paste. The gelatin apatite mixture flowed easily while the collagen apatite one was too viscous. The paste formed by the different mixtures was packed individually in thin plastic tubes and calcined at 800°C. The ashing away of the organic matter and the phase transformation of the phosphate resulted in rod shaped calcium phosphate rods. The chitosan apatite paste gave the most uniform rods of good porosity. The calcined samples were analysed for their chemical and physical properties. Characterisation was done by FT IR and X-ray diffraction. The material was stable in water and in a phosphate buffer and did not disintegrate. The water uptake and chitosan solution uptake were determined. The porous rods were brittle with comparatively poor bending strength. The apatite rods loaded with an antibiotic like gentamicin sulphate is intended to be used for drug delivery at the sites of orthopaedic implants for the prevention of osteomyelitis
    Engineering in Medicine and Biology Society, 1995 and 14th Conference of the Biomedical Engineering Society of India. An International Meeting, Proceedings of the First Regional Conference., IEEE; 01/1995