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C G Suresh

Publications and source records attributed to C G Suresh.

15 recordsLinked to original sources
PubMed1996

Ancestry and interrelationships of the Indians and their relationship with other world populations: a study based on mitochondrial DNA polymorphisms.

Mitochondrial DNA variation was studied in 100 Indians using the same set of six restriction enzymes used in the study of other world ethnic groups in order to compare and discern possible relationships of the Indian populations. Twenty nine mtDNA types were found including the ones from an earlier study (Semino et al. 1991) and unweighted pair-group method (UPGMA) and maximum parsimony trees were constructed using the mtDNA types. The nucleotide diversity values were calculated using the maximum likelihood method. From a study of the shared mitochondrial DNA types and the parsimony tree (Fig. 2) we came to the conclusion that the Indian population is closer to Caucasians and has an admixture with Asians. The North Indian population appears to have a recent admixture of the Caucasian mtDNA types which is absent in the south.

DNA, Mitochondrial↗
PubMed1995

The crystal structure of a cyanogenic beta-glucosidase from white clover, a family 1 glycosyl hydrolase.

BACKGROUND: beta-glucosidases occur in a variety of organisms and catalyze the hydrolysis of aryl and alkyl-beta-D-glucosides as well as glucosides with only a carbohydrate moiety (such as cellobiose). The cyanogenic beta-glucosidase from white clover (subsequently referred to as CBG) is responsible for the cleavage of cyanoglucosides. Both CBG and the cyanoglucosides occur within the plant cell wall where they are found in separate compartments and only come into contact when the leaf tissue experiences mechanical damage. This results in the eventual production of hydrogen cyanide which acts as a deterrent to grazing animals. beta-glucosidases have been assigned to particular glycosyl hydrolase families on the basis of sequence similarity; this classification has placed CBG in family 1 (there are a total of over 40 families) for which a three-dimensional structure has so far not been determined. This is the first report of the three-dimensional structure of a glycosyl hydrolase from family 1. RESULTS: The crystal structure of CBG has been determined using multiple isomorphous replacement. The final model has been refined at 2.15 A resolution to an R factor of 18.9%. The overall fold of the molecule is a (beta/alpha)8 [or (alpha/beta)8] barrel (in common with a number of glycosyl hydrolases) with all residues located in a single domain. CONCLUSIONS: Sequence comparisons between beta-glucosidases of the same family show that residues Glu183 and Glu397 are highly conserved. Both residues are positioned at the end of a pocket located at the C terminus of the barrel and have been assigned the respective roles of proton donor and nucleophile on the basis of inhibitor-binding and mutagenesis experiments. These roles are consistent with the environments of the two residues. The pocket itself is typical of a sugar-binding site as it contains a number of charged, aromatic and polar groups. In support of this role, we present crystallographic data on a possible product complex between CBG and glucose, resulting from co-crystallization of the native enzyme with its natural substrate, linamarin.

Binding Sites↗
PubMed1994

Warfarin treatment and migraine.

A patient suffering from migraine, whose symptoms were abolished by warfarin therapy, is reported. Warfarin was prescribed for deep vein thrombosis and the frequency of the patient's headache improved remarkably during the anticoagulant therapy. Because of the unusual nature of the response to anticoagulant therapy, warfarin was reintroduced on a double blind (versus placebo) basis and once again abolished the headaches.

Aged↗
PubMed1993

Late symptom recurrence after successful coronary angioplasty: angiographic outcome.

OBJECTIVES: To determine the angiographic appearance of the dilated coronary artery and the cause of symptoms in patients who presented with a return of chest pain more than 1 year after successful percutaneous transluminal coronary angioplasty (PTCA). DESIGN: Retrospective analysis of coronary angiograms and review of case histories. PATIENTS AND METHODS: 112 patients who underwent repeat coronary arteriography for investigation of chest pain 13-105 (median, 30) months after successful coronary angioplasty were studied. All patients were free of symptoms for at least 12 months after the initial angioplasty. RESULTS: A return of chest pain was attributed to restenosis in 12 patients (11%), to a new lesion or worsening of pre-existing coronary lesion in 56 patients (50%), and to both restenosis and stenosis in non-dilated coronary segments in 10 patients (9%). There was no restenosis in 112 of the 134 dilated lesions (84%). In 34 patients (30%), there was no significant stenosis in either dilated or non-dilated coronary segments. CONCLUSIONS: In patients undergoing coronary angiography for the investigation of recurrent chest pain more than 1 year after successful coronary angioplasty, the majority of dilated coronary segments had a good angiographic appearance. Late onset angina following PTCA is usually due to new coronary lesions or worsening of pre-existing mild stenosis.

Angina Pectoris↗
PubMed1990

Crystal structure of low humidity tetragonal lysozyme at 2.1-A resolution. Variability in hydration shell and its structural consequences.

Tetragonal crystals of hen egg white lysozyme undergo a reversible transformation, accompanied by loss of water, when the relative humidity of the environment is reduced to about 90%. The structure of the low humidity form has been analyzed, using x-ray data collected at 88% relative humidity, in order to explore the variability in protein hydration caused by a change in the amount of water surrounding the protein molecule and the consequent conformational perturbations in the molecule. The structure has been refined by the restrained least-squares method to an R value of 0.162 for 6269 observed reflections in the 10-2.1-A resolution shell. The refined structure provides interesting examples for the variability in helical parameters, the role of interactions involving side chains and water in the stabilization of secondary structural features, and favorable specific hydration sites. The protein molecule as a whole moves slightly in the low humidity form from its position in the native crystals. The hydration shell tends to move along with the protein. Significant changes, however, occur in the hydration shell. These changes cause structural perturbations in the enzyme molecule, which are most pronounced in regions involved in substrate binding.

Animals↗
PubMed1988

X-ray studies on crystalline complexes involving amino acids and peptides. XV. Crystal structures of L-lysine D-glutamate and L-lysine D-aspartate monohydrate and the effect of chirality on molecular aggregation.

L-Lysine D-glutamate crystallizes in the monoclinic space group P2(1) with a = 4.902, b = 30.719, c = 9.679 A, beta = 90 degrees and Z = 4. The crystals of L-lysine D-aspartate monohydrate belong to the orthorhombic space group P2(1)2(1)2(1) with a = 5.458, b = 7.152, c = 36.022 A and Z = 4. The structures were solved by the direct methods and refined to R values of 0.125 and 0.040 respectively for 1412 and 1503 observed reflections. The glutamate complex is highly pseudosymmetric. The lysine molecules in it assume a conformation with the side chain staggered between the alpha-amino and the alpha-carboxylate groups. The interactions of the side chain amino groups of lysine in the two complexes are such that they form infinite sequences containing alternating amino and carboxylate groups. The molecular aggregation in the glutamate complex is very similar to that observed in L-arginine D-aspartate and L-arginine D-glutamate trihydrate, with the formation of double layers consisting of both types of molecules. In contrast to the situation in the other three LD complexes, the unlike molecules in L-lysine D-aspartate monohydrate aggregate into alternating layers as in the case of most LL complexes. The arrangement of molecules in the lysine layer is nearly the same as in L-lysine L-aspartate, with head-to-tail sequences as the central feature. The arrangement of aspartate ions in the layers containing them is, however, somewhat unusual. Thus the comparison between the LL and the LD complexes analyzed so far indicates that the reversal of chirality of one of the components in a complex leads to profound changes in molecular aggregation, but these changes could be of more than one type.

Aspartic Acid↗
PubMed1987

Subdural empyema.

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Adolescent↗
PubMed1983

Occurrence and geometrical features of head-to-tail sequences involving amino acids in crystal structures.

A careful study of the crystal structures of commonly occurring amino acids, and their racemates and complexes reveals that each hydrogen bond connecting the alpha-amino and the alpha-carboxylate groups and its symmetry equivalents generally give rise to an infinite head-to-tail sequence in which the two groups are periodically brought into close proximity. Such sequences, which have earlier been suggested to be of probable relevance to prebiotic polymerisation, appear to be an almost universal feature of amino acid aggregation in the solid state. These sequences belong to two main categories in terms of the geometrical arrangement of amino acid molecules in them. The sequences in the first category consist of straight chains of molecules related mostly by the shortest cell translation in the crystals. The sequences of the second category form hydrogen bonded two fold helices centred around crystallographic 2(1) screw axes. The sequences can be further sub-divided into different types on the basis of the geometrical features of the hydrogen bonds involved in them. A few sequences involving both L and D isomers have also been observed in the crystal structures of some DL-amino acids. The shortest cell translation in most crystals under consideration has a value in the neighbourhood of 5.3 A and corresponds to the periodicity of a straight head-to-tail sequence or, less frequently, that of a helical sequence or both. The crystal structures of amino acids and their complexes can be classified in terms of the occurrence and the geometrical disposition of different types of head-to-tail sequences in them.

Amino Acid Sequence↗
PubMed1983

X-ray studies on crystalline complexes involving amino acids and peptides. X. Head-to-tail sequences in the crystal structure of L-lysine acetate.

L-Lysine acetate crystallises in the monoclinic space group P21 with a = 5.411 (1), b = 7.562(1), c = 12.635(2) A and beta = 91.7(1) degrees. The crystal structure was solved by direct methods and refined to an R value of 0.049 using the full matrix least squares method. The conformation and the aggregation of lysine molecules in the structure are similar to those found in the crystal structure of L-lysine L-aspartate. A conspicuous similarity between the crystal structures of L-arginine acetate and L-lysine acetate is that in both cases the strongly basic side chain, although having the largest pK value, interacts with the weakly acidic acetate group leaving the alpha-amino and the alpha-carboxylate groups to take part in head-to-tail sequences. These structures thus indicate that electrostatic effects are strongly modulated by other factors so as to give rise to head-to-tail sequences which have earlier been shown to be an almost universal feature of amino acid aggregation in the solid state.

Amino Acids↗
PubMed1983

X-ray studies on crystalline complexes involving amino acids and peptides. VIII. Head-to-tail arrangement and a specific interaction in the crystal structure of L-arginine acetate.

L-Arginine acetate crystallizes in the monoclinic space group P2(1) with a = 9.229(2), b = 5.178(3), c = 13.271(4) A and beta = 111.4(1) degrees. The crystal structure was solved by direct methods and refined to an R value of 0.058 for 1333 observed reflections. The conformation of the arginine molecules in the crystal is different from those observed in the crystals of L-arginine, its salts and complexes. The crystal structure indicates that complexation with a small carboxylic acid like acetic acid is sufficient to align arginine molecules in a head-to-tail fashion. The structure contains a specific ion-pair interaction, involving electrostatic attraction as well as two nearly parallel, N-H ... O hydrogen bonds, between the guanidyl group and the acetate ion.

Acetates↗