Showing papers by "University of Madras published in 1972"

Conformational studies of -glucans.

Abstract: A study of the effect of linkage on the possible conformations of di-and polysaccharides of α -D-glucose and also the probable intramolecular hydrogen bonds has been made. The differences in the nature of linkage is shown to effect the energetically preferred conformations; (1 → 2) linkages lead only to righthanded helical conformations, (1 → 3) linkages lead to extended as well as both left and righthanded helical conformations; (1 → 4) linkages lead to both right-and lefthanded wide helical conformations. The possible hydrogen bonds between adjacent residues are also dependent on the nature of the linkage. A comparison of the conformational data of α-D-glucans with those of β -D-glucans has indicated that the favored conformations and hydrogen bonds between contiguous residues in the chain are influenced by the configuration at the anomeric carbon atom in all the three types of polysaccharides. From the energy calculations a probable conformation (φM = -10°, ΨM = -30°, φN = -23°, ΨN = -19°) has also been proposed for crystalline mycodextran in conformity with x-ray data. This conformation contains two types of hydrogen bonds between contiguous residues one between 0-2 and 0-3 atoms at (1 → 4) linkage and the other between 0-2 and 0-4 atoms at (1 → 3) linkage in the chain. The conformation of maltose unit (-10°,-30°) that is likely to occur in the crystalline mycodextran coincides with the minimum energy conformation of maltose.

Hormonal rupture of larval diapause in the tick rhipicephalus sanguineus (Lat.).

Abstract: Die Diapause von Larven der ZeckeRhipicephalus sanguineus (Lat.) wird durchα- andβ-Ecdyson beendet.

On the apparent visual forms of relativistically moving objects

Abstract: The question of the apparent visual shape of an object moving at relativistic speeds, as perceived by a single observer, is analysed afresh. It is shown by qualitative arguments that the apparent shape is related to the shape at rest through a combination of nonuniform shear and extension/contraction parallel to the direction of motion, which does not reduce to a rotation even in the case of distant objects subtending a small angle at the observer. The two-dimensional projection (as in a photograph) of this distorted shape may coincide with that of the object (suitably rotated) at rest; but we emphasize that it would be grossly misleading to conclude from this, as is generally done in the literature, that distant relativistically moving objects appear as if simply lotated. The « train paradox » is discussed in illustration of this point. Analytical formulae relating the apparent visual shape to the shape at rest are given. Also the striking fact that the apparent speed of the object as seen by visual observation may well exceed the speed of light is brought out. Finally it is pointed out that the phenomenon is closely analogous to the relativistic Doppler effect.

Termite Queen Substance: 9-Oxodec- trans -2-enoic Acid

Abstract: EXTRACTS of honeybee (Apis mellifera) queens inhibit the development of supplementary reproductives in the termite, Kalotermes flavicollis1. Similarly, extracts of a whole queen of the termite, Odontotermes genus2, and queen heads of O. assmuthi inhibit queen rearing by workers of A. mellifera2 and A. cerana (unpublished work of A. S. et al.) and also development of the workers' ovaries of these species. These observations indicate that the “queen substance” of honeybees and termites exhibits reciprocal activity, and suggest that the chemical nature of the queen substance of termites may be 9-oxodec-trans-2-enoic acid of A. mellifera3, A. cerana, A. dorsata4,5 and A. florea5 or a similar substance; but the queens of termites have not yet been unequivocally shown to contain queen substance. We have made extracts of physogastric queen heads of the mound-building termite, O. assmuthi, and have analysed these extracts qualitatively for queen substance.

Respiratory metabolism of crabs from marine and estuarine habitats. I. Scylla serrata

Abstract: Nearly 500 crabs, Scylla serrata (Forskal) (family Portunidae), ranging in wet weight from 0.2 to 14.0 g, were acclimated to 27° and 35°C and their respiratory metabolism under water and on exposure to air at test temperatures ranging from 16° to 38°C was studied. In aquatic respiration, the response to temperature of crabs acclimated to a temperature of 16°C is statistically significant, and directly related to their weight. Smaller crabs did not survive at the warm acclimation level of 35°C. The metabolic rates of cold-adapted S. serrata are higher than those of warm-adapted ones. The effect of acclimation to aerial respiration on crabs acclimated to cold temperature varied slightly between large and small crabs. The aerial respiration rate was less than a tenth of the aquatic rate for all sizes. The response of S. serrata to warm acclimation in air has been found to be almost opposite to its response in water.

An Evaluation of the Metachromasia of Bromophenol Blue

Abstract: The heterogeneity of bromophenol blue from different commercial sources was revealed by paper chromatography. Isopropanol:ammonia:water (20:1:2) as the solvent system gave the best separation. A variety of impurities: violet, pink, light blue and yellow coloured ones were observed. Two of the yellow fractions showed a spectral shift to red in the presence of ammonia vapour. The respone of the main dye component with the anionic chromotropes such as heparin and hyaluronate was found to be metachromatic similar to that exhibited by the dye solution and not due to a polychromatic effect. The metachromatic effect was blocked by FeCl3 as in the case of cationic dye metachromasy. The observed metachromatic colour is not one of the colours which characterize those resulting from changes caused by pH.

Configurational statistics of polysaccharides. VI. Linear (1→4)-linked galactan†

Abstract: The conformational energies for (1→4)-linked α -D- and β -D-galactans have been computed by considering nonbonded, torsional, and electrostatic interactions. The electrostatic interactions are estimated by assigning the charges to various atoms in the molecule by the method of Del Re. The characteristic ratios C N = 〈r 2 〉 0 /Nl v 2 are computed for α -D- and β -D-galactans as a function of the degree of polymerization N and the angle Τ at the bridge oxygen atom. These values of characteristic ratios obtained for α -D-galactan are very much higher than for β -D-galactan, indicating that the former assumes a highly extended conformation compared to the latter. The values of characteristic ratios of both these polysaccharides show a decrease with increase in Τ similar to that observed for other (1→4)-linked polysaccharides. The calculated values of C ∞ of (1→4)-linked polysaccharides show no correlation with the number of allowed conformations but are affected both by the orientation of the interunit glycosidic bonds and the hindered potential associated with chain units. It has also been shown that the magnitude of the steric factor σ may not be used as an index of flexibility for polysaccharides which differ in type of linkage.

Some performance characteristics of spray columns

Abstract: Experimental data on the drop size distribution obtained from multiple nozzles in a spray column are presented and analyzed. For nozzles having a diameter above the critical size, the distribution pattern change from near normal monomodal to bimodal and back again to monomodal but skewed toward the larger size fraction. There is no change in the observed maximum drop size in the distribution with flow rate except near the critical velocity region. Drop breakup mechanisms appear to be different from the above pattern for nozzles below a critical size. A model is proposed for prediction of the complete range of drop sizes observed.

Wave equations for zero-mass particle with invariant helicities

Abstract: We present a brief discussion of the difficulties associated with taking the limitm→0 in massive-particle equations of the formi(∂ψ/∂t)=Hψ, in which ψ transforms according to theD(0,s)⊕D(s,0) representation of the homogeneous Lorentz group. It is pointed out that, though the HamiltonianH tends to a well-defined form asm→0, the resulting wave equation is still unsatisfactory as the invariant scalar product (in the space of solutions of the wave equation) has an unacceptable form. We observe that this difficulty is due to the indecomposability of the representation of the Poincare group over wave functions transforming asD(0,s)⊕D(s,0) in the massless case. Making due allowance for this fact we obtain, in close parallel to the treatment for massive particles, wave equations for zero-mass particles with invariant helicities ±s. The relevant invariant scalar products are also determined.

Studies in molecular structure, symmetry and conformation VI. Crystal and molecular structure of 1-aminocyclopentane carboxylic acid monohydrate

Abstract: 1-aminocyclopentane carboxylic acid monohydrate is monoclinic: space groupP21/c,a = 11·24,b = 6·27,c = 11·22 A and β = 97·6 °. The crystal structure was solved by the symbolic addition method and refined to anR factor of 12·1%. The cyclopentane ring is disordered; one of the carbon atoms exists in two alternative sites, leading to two possible conformations both of which are of the envelope type.

Further studies in Saccharum-zea hybrid I. Mitotic studies

Abstract: THE first intergeneric hybrid in Saccharum was made in 1913 by C. S. Barber at Coimbatore. He crossed S. officinarum var. Vellai (2n = 80) with Xarenga porphyrocoma (2n 30) and obtained two types of hybrids. One (2n =95) had a diploid gamete of S. qfficinarum (2n = 80). The other (2n = 55) had only the haploid gamete (n = 40). The same variety of S. officinarum was pollinated with Zea mays var. Golden Beauty which had two additional B chromosomes, by E. K. Janaki Ammal in 1938. A single seedling was the outcome. It had 52 chromosomes, being the sum of the haploid complements of Saceharum (n =40) and of Zea (n = 10) with the two B chromosomes of maize (Janaki Ammal, 1941). Tillering was most abundant and the plant which was clonally propagated survived 30 years but without producing any inflorescence. This failure to produce \"arrows\" was found to be due to the non-emergence of the inflorescence out of the boot leaf which when dissected was found to be lying within the flag leaf. Naidu and Ramakrishnan (1970) induced the inflorescence to emerge by the application of gibberelic acid and it was found to be similar to that of Saccharuni (figs. 1 and 2). A fourth glume which does not occur in either parent was present in the hybrid, though some of the S. officinarurn clones do have one. There were three stamens as in the parents.

Covariant wave functions with invariant helicity for massless particles

Abstract: Considering a wave functionψ for a massless particle, transforming according to an arbitrary irreducible representation (IR) of the homogeneous Lorentz group, we determine the basic conditions forψ to be an eigenfunction with a specified valueλ of the helicity inall Lorentz frames. The method used is direct and elementary, requiring no knowledge of the IR's of the Poincare group. It is shown that there existsno invariant helicity state in unitary representations of the Lorentz group, and one such state in any non-unitary representation (with one extra in special cases).

Conformation of random polypeptide chains

Abstract: The characteristic ratios C of and C ∞ are calculated for infinitely long poly(L-amino acid) chains having a-CH 2 -R' substitution at the C α atom, as functions of the valence angle τ at the C α atom. The value of C of is found to increase from 1.6 to 2.3 as τ varies from 105 to 115°. On the other hand, C α decreases with increasing τ in the range 105-111°, passes through a minimum at 111°, and then increases slowly. Since, C ∞ is much less dependent on τ in the most commonly observed range (110-115°), any variation in τ in this range due to solvent would not appreciably affect C ∞ . The calculated temperature coefficient of C ∞ is negative and increases significantly in absolute magnitude even for small deviations in τ from 110°.

Beta spectrum of140La

Abstract: The β spectrum of140La has been analysed with a thoroughly tested Slatis-Siegbahn β-ray spectrometer equipped with a well-type plastic whose counting efficiency is unity down to 50 keV. The F.K. analysis in which the outer group is properly shape-corrected yields β groups: (2164±2) (8%), (1680±7) (18%), (1365±10) (46%), (1150±5) (19%), (857±15) (4%) and (510±20) (5%) keV. The outer β group with end point 2164 keV has « modifiedB ij shape » withD =2.3 ± 2, indicative of complete cancellation in the matrix element combinationY. The experimental shape supports the (g 7/2) J =2/2 proton configuration to the 2+ first excited level of140Ce, but a quantitative agreement is possible only when the CVC condition is relaxed.

Free amino acids in the haemolymph ofEoperipatur weldoni (onychophora)

Abstract: Mit der Methodk nach Folin und Spackmann wurden die Freien Aminosauren in der Hamolymphe vonEoperipatus weldoni festgestellt und in ihrer Gesamtkonzentration mit den Aminosaren der Myriapoden und primitiven hemimetabolischen Insekten vergleichbar gefunden.

Paper Chromatographic Separation of Arsenic Valences

Abstract: Separation of As(III) from As(V) by paper chromatography is described The choice of suitable eluent is indicated An explanation is offered for the observed separation on the basis of complexation and solvation of the arsenic ions