The Isolation and Characterization of β-N-Oxalyl-L-α,β-Diaminopropionic Acid: A Neurotoxin from the Seeds of Lathyrus sativus

A neurotoxic compound has been isolated from the seeds of Lathyrus sativus in 0.5% yield and characterized as β-N-oxalyl-L-α,β-diaminopropionic acid. The compound is highly acidic in character and forms oxalic acid and diaminopropionic acid on acid hydrolysis. The compound has a specific rotation of -36.9° and has apparent pK values in the order of 1.95, 2.95, and 9.25, corresponding to the two carboxyl and one amino functions, respectively. The compound has been synthesized by reacting an aqueous methanolic solution of the copper complex of L-α,β-diaminopropionic acid prepared at pH 4.5-5.0 with dimethyl oxalate under controlled pH conditions and isolating the compound by chromatography on a Dowex 50-H+ column after precipitating the copper. The compound induced severe neurological symptoms in day-old chicks at the level of 20 mg/chick, but not in rats or mice. It also inhibited the growth of several microorganisms and of the insect larva Corcyra cephalonica Staint. L-Homoarginine had no neural action in chicks. It is suggested that the neurotoxic compound is species specific in its action and may be related to "neurolathyrism" associated with the human consumption of L. sativus seeds.

Estimation of signals in colored non gaussian noise based on Gaussian Mixture models

Non-Gaussianity of signals/noise often results in significant performance degradation for systems, which are designed using the Gaussian assumption. So non-Gaussian signals/noise require a different modelling and processing approach. In this paper, we discuss a new Bayesian estimation technique for non-Gaussian signals corrupted by colored non Gaussian noise. The method is based on using zero mean finite Gaussian Mixture Models (GMMs) for signal and noise. The estimation is done using an adaptive non-causal nonlinear filtering technique. The method involves deriving an estimator in terms of the GMM parameters, which are in turn estimated using the EM algorithm. The proposed filter is of finite length and offers computational feasibility. The simulations show that the proposed method gives a significant improvement compared to the linear filter for a wide variety of noise conditions, including impulsive noise. We also claim that the estimation of signal using the correlation with past and future samples leads to reduced mean squared error as compared to signal estimation based on past samples only.

Ambiguity-free polarization measurements from mixture initial preparations

Starting from beam and target spin systems which are polarized in the usual way by applying external magnetic fields, measurements of appropriate final state tensor parameters, viz., {t0,1k, k=1,...,2j} of particle d with spin j in a reaction a+b→d+c1+c2+. . .are suggested to determine the reaction amplitudes in spin space free from any associated discrete ambiguity.

Crystallization and preliminary X-ray studies of a galactose-specific lectin from the seeds of bitter gourd (Momordica charantia)

A galactose-specific lectin from the seeds of bitter gourd (Momordica charantia) is a four-chain type II ribosome-inactivating protein (RIP) resulting from covalent association through a disulfide bridge between two identical copies of a two-chain unit. The available structural information on such four-chain RIPs is meagre. The bitter gourd lectin was therefore crystallized for structural investigation and the crystals have been characterized. It is anticipated that the structure of the orthorhombic crystals will be analysed using molecular replacement by taking advantage of its sequence, and presumably structural, homology to normal two-chain type II RIPs.

Triacylglycerol synthesis in developing seeds of groundnut (Arachis hypogaea): Pathway and properties of enzymes of sn-Glycerol 3-phosphate formation

The enzymatic pathway for the synthesis of sn-glycerol 3-phosphate was investigated in developing groundnut seeds (Arachis hypogaea). Glycerol-3-phosphate dehydrogenase was not detected in this tissue but an active glycerokinase was demonstrated in the cytosolic fraction. It showed an optimum pH at 8.6 and positive cooperative interactions with both glycerol and ATP. Triosephosphate isomerase and glyceraldehyde-3-phosphate phosphatase were observed mainly in the cytosolic fraction while an active glyceraldehyde reductase was found mainly in the mitochondrial and microsomal fractions. The glyceraldehyde 3-phosphate phosphatase showed specificity and positive cooperativity with respect to glyceraldehyde 3-phosphate. The glyceraldehyde reductase was active toward glucose and fructose but not toward formaldehyde and showed absolute specificity toward NADPH. It is concluded that in the developing groundnut seed, sn-glycerol 3-phosphate is synthesized essentially by the pathway dihydroxyacetone phosphate ? glyceraldehyde 3-phosphate ?Pi glyceraldehyde ?NADPH glycerol ?ATP glycerol 3-phosphate. All the enyzmes of this pathway showed activity profiles commensurate with their participation in triacylglycerol synthesis which is maximal during the period 15�35 days after fertilization. Glycerokinase appears to be the rate-limiting enzyme in this pathway.

Enhanced Pair Hydrophobicity in the Water-Dimethylsulfoxide (DMSO) Binary Mixture at Low DMSO Concentrations

We observe a surprisingly sharp increase in the pair hydrophobicity in the water climethylsulfoxide (DMSO) binary mixture at small DMSO concentrations, with the mole fraction of DMSO (x(D)) in the range 0.12-0.16. The increase in pair hydrophobicity is measured by an increase in the depth of the first minimum in the potential of mean force (PMF) between two methane molecules. However, this enhanced hydrophobicity again weakens at higher DMSO concentrations. We find markedly unusual behavior of the pure binary mixture (in the same composition range) in the diffusion coefficient of DMSO and in the local composition fluctuation of water, We find that, in the said composition range, the average coordination number of the methyl groups (of distinct DMSO) varies between 2.4 and 2.6, indicating the onset of the formation of a chain-like extended connectivity in an otherwise stable tetrahedral network comprising of water and DMSO molecules. We propose that the enhanced pair hydrophobicity of the binary mixture at low DMSO concentrations is due to the participation of the two methane molecules in the local structural order and the emerging molecular associations in the water-DMSO mixture.

Calorimetry In Vapor Absorption And Binary Mixture Vapor Compression Refrigeration And Heatpump Systems

The use of binary fluid systems in thermally driven vapour absorption and mechanically driven vapour compression refrigeration and heatpump cycles has provided an impetus for obtaining experimental date on caloric properties of such fluid mixtures. However, direct measurements of these properties are somewhat scarce in spite of the calorimetric techniques described in the literature being quite adequate. Most of the design data are derived through calculations using theoretical models and vapour-liquid equilibrium data. This article addresses the choice of working fluids and the current status on the data availability vis-a-vis engineering applications. Particular emphasis is on organic working fluid pairs.

Carbon-13 NMR studies of lipid mobilization pattern in germinating groundnut (Arachis hypogaea L.) seeds

The products of lipid mobilization in groundnut (Arachis hypogaea L.) seeds as a function of time immediately after imbibition are monitored by 13C NMR. Different parts of the embryonic axis, namely,the radicle, hypocotyl, and plumule, exhibit characteristic time dependent 13C NMR spectra observed at 24-h intervals after imbibition. The various stages in the transformation of storage lipids present in different parts of the embryonic axis are clearly demonstrated. The transformaton of storage lipids is completed first in the radicle followed by the hypocotyl and finally the plumule. A mechanism of the transformation of the storage lipids is discussed.