Showing papers by "University of Madras published in 1977"
TL;DR: A new method for mapping the folding of the backbone polypeptide chain of protein molecules is presented, which brings out all the features of protein folding, with no degeneracy caused by depicting the conformational details, and is useful in readily recognising all the secondary structures, without ambiguity, as one progresses along the chain.
Abstract: CONFORMATIONAL details of small molecules can easily be visualised in the usual stereo diagrams used by crystallographers, but such details cannot be readily visualised for protein molecules made up of thousands of atoms. For such large molecules special types of representations become necessary for depicting their three-dimensional structure, in the form of two-dimensional diagrams. In view of this, many attempts to represent the conformational details in protein molecules, have been reported1–7. I present here a new method for mapping the folding of the backbone polypeptide chain of protein molecules. This representation brings out all the features of protein folding, with no degeneracy caused by depicting the conformational details, and is useful in readily recognising all the secondary structures, without ambiguity, as one progresses along the chain.
43 citations
39 citations
TL;DR: An analysis of secondary sexual characters in post-larval juveniles during megalopa settlement corroborates the view that males and females develop separately from the megalOPA.
Abstract: Male Emerita asiatica Milne Edwards are smaller than females. The secondary sexual characters of males and females are described in detail. Applying the method of Wenner (1972), sex ratio is calculated. The overlap in size range between males and females is too wide to suggest sex reversal. An analysis of secondary sexual characters in post-larval juveniles during megalopa settlement corroborates the view that males and females develop separately from the megalopa. The males acquire their sexual maturity soon after metamorphosis from the megalopa stage, whereas the females attain their sexual maturity only after considerable body growth. the males continue to grow to attain a maximum carapace length of 11 mm; they do not show any tendency towards changing their sex. This is evidenced by the fact that the weight increase of the gonadal apparatus is directly related to the increase in the male carapace length (CL) and body weight. On the other hand, retention of larval characters such as short eye stalk, toothless chelae of the fifth leg (in males up to 5 mm CL), together with the very small size suggest that the males are neotenic. Only males up to 5 mm CL were found to take part in mating. During mating, as many as 5 tiny males deposit their spermatophores in the pleopodal region of one female. This type of mating assures effective transfer of spermatophores in the turbulent environment inhabited. Spermatophores are pedunculate and embedded in a gelatinous matrix to form a long ribbon. There are two types of spermatophores in the ribbon, and they differ in detail from those of other anomuran species. The spermatozoa are rod-like, with a club-shaped acrosomal head. Five spines originate from the junction between head and body. The mode of sperm release from the spermatophores is described; oviducal secretion may be responsible for opening the spermatophore.
36 citations
TL;DR: In this paper, the polymerization of acrylonitrile was studied in aqueous sulfuric acid with the redox initiator system, ceric ammonium sulfate/glycerol at 15-25°C.
Abstract: The polymerization of acrylonitrile was studied in aqueous sulfuric acid with the redox initiator system, ceric ammonium sulfate/glycerol at 15–25°C. The initiation was effected by the ceric ion and the radical produced from the reaction of Ce4+ with glycerol. At lower concentrations of Ce4+, the rate of monomer disappearance was proportional to [M]1,5, [G]0,5, and [Ce4+]0,5, and the rate of ceric ion disappearance was directly proportional to [Ce4+] and [G]. The results were explained by a kinetic scheme involving the oxidation of substrate by Ce4+ to give the primary radical and further reaction of the latter with Ce4+ to give the final product, and initiation of polymerization both by Ce4+ and the primary radical. The initiation by Ce4+ was found to be negligible as compared to that by the primary radical. The termination step is postulated to be mutual at lower concentrations of Ce4+ and linear at higher concentrations of Ce4+. The induction period and the rate of polymerization was compared with those of other polyol systems, such as sorbitol and mannitol.
24 citations
TL;DR: In this article, the stability constants for complexes formed by uranyl ion with amino acids were determined by pH titrations at 31°C and μ = 0.1 (NaClO 4 ) in the pH rang 1.7-3.5.
12 citations
11 citations
TL;DR: The present study indicates that the plasmatocytes reported by previous workers may be the altered granular haemocytes, and the mode of formation of vacuolar droplets together with the association of granules with them suggests secretory activity of the haemocyte.
Abstract: The characteristics of granular haemocytes of four non-insect arthropods were compared. The refractile, bacilliform granular inclusions dissolve in aqueous solutions of dyes. On glass slides, the cytoplasm of the haemocyte becomes distinctly separated into agranular ectoplasm with well developed filopodia and granular endoplasm. The mode of formation of vacuolar droplets together with the association of granules with them suggests secretory activity of the haemocytes. Fragmentation of cytoplasm or clasmatosis is common feature of granular haemocytes from prechilled animals. The significance of clasmatosis is discussed.The present study indicates that the plasmatocytes reported by previous workers may be the altered granular haemocytes. The characteristics of granular haemocytes of arthropods are compared with that of the granulocytes of molluscs.
10 citations
TL;DR: In this article, it was observed that the hardress of the irradiated crystal increases with the increase in the total dosage of irradiation, and distortion of lattice was observed.
Abstract: Calcite single crystals on neutron bombardment change their colour to pale red, red and deep red, as the duration of irradiation increases. The irradiated surface becomes rugged and on etching, a large number of micropits are observed. Using Vicker’s hardness indenter, it is observed that the hardress of the irradiated crystal increases with the increase in the total dosage. From Laue x-ray diffraction studies of irradiated crystals, distortion of lattice is observed. Absorption spectra in the visible region show an extra peak for irradiated samples which is absent for radiated ones. The radiation effects are annealed to a considerable extent on heat treatment. The implications are discussed.
9 citations
TL;DR: Details of the new methods of analysis of chain folding characterization of proteins proposed earlier and their application to six proteins and results pertaining to the angles θ and δ are presented are presented.
9 citations
TL;DR: A novel description of the conformational characteristics of all the individual nucleotides and the phosphodiesters in tRNAs is presented in the form of a circular plot, obtained for yeast tRNAP.
Abstract: A novel description of the conformational characteristics of all the individual nucleotides and the phosphodiesters in tRNAs is presented in the form of a circular plot. This representation furnishes information of the base sequence with the folding patterns of the polynucleotide chain as one traverses along the circumference and with the individual nucleotide and phosphodiester linkage torsions along the radii. The circular plot obtained for yeast tRNAPhe strikingly distinguishes the helical and the loop regions. The variation of the different nucleotide torsions along the entire chain length and their effect on the secondary helical and tertiary loop regions become readily apparent.
8 citations
01 Jul 1977
TL;DR: The segmentation of the first wholly internal cell or cells may be looked upon as the first important morphogenetic event that initiates an organizational change in the reaction system of the proembryo, as it results in the differentiation of two groups of cells which thereafter follow different developmental pathways.
Abstract: The unique pattern of angiosperm embroygeny provides few meaningful criteria for classification. The existing classifications are based solely on the early segmentation pattern of the proembryo. Analysis of angiosperm proembryo with regard to change in surface to volume ratio and segmentation of internal cells, provides significant criteria for a meaningful classification.
TL;DR: The cellular nature of the capsule of the cystacanth, which contains haemocytes in response to the release of metabolites by the parasites, suggests that the capsule is of host origin.
Abstract: The nature of the capsule of the cystacanth of Moniliformis moniliformis was studied Fat body, tracheal system, Malpighian tubules and haemocytes of the host are intimately associated with the cystacanth The capsule of the cystacanth is cellular The cells encapsulating the middle and late acanthellae are granular haemocytes of the host, whereas those encapsulating the cystacanth are agranular Degranulation of haemocytes after encapsulation of the cystacanth recalls the common method for encapsulation of parasites by insect haemocytes, but a difference between the two kinds of encapsulation is that the capsule around the cystacanth does not bring about melanization nor destroys the parasite It is suggested that the surface of the parasite may have inhibitors against enzyme systems causing melanization Host haemocytes are also found in the capsular fluid The infiltration of haemocytes into the capsule may be in response to the release of metabolites by the parasites It is also suggested that the haemocytes may detoxify the parasitic metabolites Rarely, capsules containing two parasites were observed In one of the cases, one of the two cystacanths already possessed its own capsule This finding, together with the cellular nature of the capsule, suggests that the capsule is of host origin
TL;DR: In this paper, the effect of correlation has been included in the bandstructure calculation for thorium and osmium using the RAPW method, and the complete band structure and Fermi surface cross sections are obtained for both the metals using the two potentials, the one (Vs) which includes only the Slater exchange and the other (VH which includes both the exchange and correlation through Overhauser's formula (1971).
Abstract: The effect of correlation has been included in the bandstructure calculation for thorium and osmium using the RAPW method. The complete bandstructure and Fermi surface cross sections are obtained for both the metals using the two potentials, the one (Vs) which includes only the Slater exchange and the other (VH) which includes both the exchange and correlation through Overhauser's formula (1971). A comparison of the authors' results with those of the previous calculations using the traditional approximations with regard to the exchange leads to the conclusion that VH yields results in better agreement with the experimental data than those obtained with Vs although the latter may still be considered fairly reliable without any violent disagreement.
TL;DR: In this article, a Monte Carlo simulation technique using potential energy calculations is used to compute the characteristic ratios for poly(trans-N-methyl glycine), poly(cis-Nmethylglycine) and poly (cis/trans-n-methyl-glucose) polypeptides, which support the view that both cis and trans units could be present in the polymer in different proportions under different solvent conditions.
TL;DR: The methods suggested earlier for the analysis and representation of protein structural data are now extended to the helical regions in finer details to enable better handling of characterization of bends and distortions, for which statistical parameters are developed.
Abstract: The methods suggested earlier for the analysis and representation of protein structural data are now extended to the helical regions in finer details. These enable better handling of characterization of bends and distortions, for which statistical parameters are also developed. Using latest myoglobin data, best experimental parameters for the α-helix are deduced to be rN = 1.55 (0.13) A, r = 2.28 (0.12) A, rC′ = 1.70 (0.10) A, r0 = 2.02 (0.12) A, ϕ = 100.5 (2.3)°, and t = 1.495 (0.055) A.
TL;DR: The angular correlation of positron annihilation in NaCl and KCl is compared for various concentrations of F-centres produced by γ-irradiation as well as additive doping as mentioned in this paper.
Abstract: The angular correlation of positron annihilation in NaCl and KCl is compared for various concentrations of F-centres produced by γ-irradiation as well as additive doping. The intensity and the “full width at half-maximum (FWHM)“ -Γ1/2 of the narrow component are slightly different for each of the X-irradiated, electron-irradiated, γ-irradiated (light and heavy doses), and addi-tively doped crystals. The possible role of additional defect centres in trapping positrons is discussed. Also angular correlation measurements of positrons annihilating in the reversible F ⇌ F' conversion centres in equilibrium in additively coloured KCI at −100 °C are given.
Es werden die Winkelkorrelationen der Positronenannihilation in NaCl und KCI fur verschiedene Konzentrationen von F-Zentren verglichen, die sowohl durch γ -Bestrahlung als auch durch additive Verfarbung hervorgerufen wurden. Die Intensitat und die “Halbwertsbreite (FWHM)” Γ1/2 der schmalen Komponente sind leicht unterschiedlich fur die rontgenbestrahlten, elektronen-bestrahlten, γ -bestrahlten (starke und schwache Dosen) und additiv verfairbten Kristalle. Die mogliche Rolle von zusatzlichen Storstellen beim Anhaften des Positrons wird diskutiert. Dar-uber hinaus wird uber Winkelkorrelationsmessungen von Positronenannihilation an den rever-siblen F ⇌ F'-Konversionsspektren im Gleichgewicht in additiv verfarbtem KCI bei −100°C be-richtet.
TL;DR: In this paper, a residue-squaring method for perturbation problems is subjected to an exacting test in its application to the problem of diagonalising the Hamiltonian of the nonlinear oscillator with quartic anharmonicity.
Abstract: A recently-formulated residue-squaring method for perturbation problems is subjected to an exacting test in its application to the problem of diagonalising the Hamiltonian of the nonlinear oscillator with quartic anharmonicity. Unlike other methods, this new iterative diagonalisation method enables several eigenvalues to be calculated simultaneously with little more labour than for a single eigenvalue. Values obtained for the four lowest even-parity levels of the anharmonic oscillator from just two or three iterations are shown to agree well with earlier accurate calculations. An approximate analytical formula for the energy levels is also presented.
TL;DR: In this paper, the kinetics of polymerization of AAM and methacrylamide with manganese(III) acetate as thermal initiator was studied. And the reactivity of the two monomers under the same conditions was compared.
Abstract: The kinetics of polymerization of acrylamide (AAM) and methacrylamide (MAM) with manganese(III) acetate as thermal initiator was studied. In the temperature range between 303 and 313 K, the initial rate of polymerization follows the relation: v=k[Monomers] · [Initiator] ½ . The rate of initiation of the polymerization was determined from the rate of decomposition of manganese(III) acetate. The reactivity of the two monomers under the same conditions was compared.
01 Oct 1977
TL;DR: The existing fluid pressure in the tube and its collapsible nature are suggestive of the ejection of the fluid through the highly chitinous resistible duct at great force, analogous to the drilling fluid used in mechanical drilling operation.
Abstract: InPurana tigrina walk. the principal salivary system consists of several digitate lobes which are arranged in two sectors, viz. the cephalic sector and the thoracic sector, corresponding to the anterior and the posterior lobes respectively of the principal salivary gland of a generalised bug. All the lobes of both the sectors are similar in their histology and staining reactions. The accessory salivary system inP. tigrina is unique among insects. It consists of a very long convoluted, collapsible secretory tube which is more than thirty times longer and six times wider than the accessory salivary duct, the junction of the tube and the duct being indicated by a circlet of five binucleate unicellular gular glands. It is suggested that the tube serves the function of secretion and storage of watery saliva and the gular glands secrete certain material which in combination with the watery saliva, serves as stylet sheath forming material thereby favouring the penetration of the stylet fascicle into the hard bark of the stem during feeding operation. The existing fluid pressure in the tube and its collapsible nature are suggestive of the ejection of the fluid through the highly chitinous resistible duct at great force, analogous to the drilling fluid used in mechanical drilling operation.
TL;DR: In this article, a new route to furo[2,3-b]quinolines has been developed based on the use of N-arylaconamides as starting materials.
Abstract: A new route to furo[2,3-b]quinolines has been developed based on the use of N-arylaconamides as starting materials. These anilides when heated with polyphosphoric acid, readily underwent intramolecular cyclization to furnish the respective 1,2-dihydro-2-oxo-quinoline-3-acetic acids which were then transformed into the corresponding dihydrofuro[2,3-b]quinolines by literature procedures. Sequential treatment of the dihydro compound withNBS andDBU afforded the corresponding furo[2,3-b]quinoline. The NMR spectra of the furoquinolines are discussed.
TL;DR: In this paper, a method for the calculation of intramolecular nonbonded interactions based on experimental bond polarisabilities and atomic charges and transition π-charges obtained from MO calculations has been applied to the alanyl dipeptide.
Abstract: A method recently developed for the calculation of intramolecular nonbonded interactions based on experimental bond polarisabilities and atomic charges and transition π-charges obtained from MO calculations has been applied to the alanyl dipeptide. The potential energy contours in the ϕ, ψ plane obtained by this method compare favourably with those derived from the frequency of occurrence of conformations in globular proteins. An analysis of the various components of the nonbonded interaction energy indicates that the fairly frequent occurrence of conformations around ϕ = −80°, ψ=0° is presumably due to a favourable interaction of the π-polarisation.
TL;DR: In this article, the rate of decomposition of the complex, sodium bis(diethanolamine)cobaltate octahydrate, was studied at pH 7 and pH 1,6, respectively.
Abstract: The rate of decomposition of the complex, sodium bis(diethanolamine)cobaltate octahydrate was studied at pH 7 and pH 1,6, respectively. This complex was found to initiate the vinyl polymerization (polymerization of acrylamide and methacrylamide) at pH 1,6 in aqueous medium. There was no polymerization at pH > 4. The dependences of the rate of polymerization on monomer concentration, initiator concentration, temperature, and pH were studied. The overall activation energy of the polymerization reaction was calculated. A kinetic reaction scheme is proposed on the basis of the experimental data.
TL;DR: In this article, the equivalence of non-renormalizable pair interactions to a renormalizable theory was proved using Kikkawa's method, and the relation between pair interactions and non-reinormalizable theories was shown.
Abstract: By using Kikkawa’s method the equivalence of the nonrenormalizable pair interaction\(\bar \psi \psi \phi ^2 \) to a renormalizable theory is proved. Equivalence relationships between a few other nonrenormalizable and renormalizable interactions are also indicated.
TL;DR: The propagation of the action potential in contractile artrial and ventricular fibres is explained by this simulated electronic circuit which has a one-to-one correspondence for its elements with the major constituents of the cardiac fibres.
Abstract: The propagation of the action potential in contractile artrial and ventricular fibres is explained by this simulated electronic circuit which has a one-to-one correspondence for its elements with the major constituents of the cardiac fibres. The phenomenon of the transient negative conductance of sodium during cell depolarisation is simulated by an active element, the planar transistor, worked in the low-voltage avalanche-reverse mode. By using such an element, the capacitive coupling via ‘nexus’ junctions has also been simulated. Further, it was found possible to demonstrate and explain some of the cardiac pathological conduction disturbance situations.
TL;DR: Hormones like cyclic AMP, prostaglandin E1 and parathyroid hormone reversed the decreased enzyme activity due to citrinin poisoning in mouse and rabbit and favours the possible existence of active and inactive forms of alkaline phosphatase in the system.
Abstract: The effect of citrinin poisoning on rabbit kidney alkaline phosphatase was investigated. After seven days administration of citrinin (2 mg/kg body weight daily) the animals were sacrificed and the level of enzymes estimated in serum and kidney. Serum enzymes showed no variation in activity in the citrinin-treated animals, but in kidney, alkaline phosphatase activity decreased significantly. The decreased activity was mainly associated with the cytoplasmic fraction and in fractions Ib and II. The enzyme II obtained from citrinin-treated animal showed no kinetic difference in substrate specificity, inhibition by phenylalanine, phosphate, sodium-EDTA and Zn2+ ions, activation by Mg2+ ions, thermal inactivation and electrophoretic mobility to that of control Enzyme II. Immunological studies showed that the decrease in enzyme activity was due to existence of inactive enzyme protein. Hormones like cyclic AMP, prostaglandin E1 and parathyroid hormone reversed the decreased enzyme activity due to citrinin poisoning in mouse and rabbit. This study favours the possible existence of active and inactive forms of alkaline phosphatase in the system.