Crystal structure of eosinophil cationic protein at 2.4 A resolution

Eosinophil cationic protein (ECP) is located in the matrix of the eosinophil's large specific granule and has marked toxicity for a variety of helminth parasites, hemoflagellates, bacteria, single-stranded RNA virus, and mammalian cells and tissues. It belongs to the bovine pancreatic ribonuclease A (RNase A) family and exhibits ribonucleolytic activity which is about 100-fold lower than that of a related eosinophil ribonuclease, the eosinophil-derived neurotoxin (EDN). The crystal structure of human ECP, determined at 2.4 A, is similar to that of RNase A and EDN. It reveals that residues Gln-14, His-15, Lys-38, Thr-42, and His-128 at the active site are conserved as in all other RNase A homologues. Nevertheless, evidence for considerable divergence of ECP is also implicit in the structure. Amino acid residues Arg-7, Trp-10, Asn-39, His-64, and His-82 appear to play a key part in the substrate specificity and low catalytic activity of ECP. The structure also shows how the cationic residues are distributed on the surface of the ECP molecule that may have implications for an understanding of the cytotoxicity of this enzyme.     

Dimerization specificity of all 67 B-ZIP motifs in Arabidopsis thaliana: a comparison to Homo sapiens B-ZIP motifs

Basic region-leucine zipper (B-ZIP) proteins are a class of dimeric sequence-specific DNA-binding proteins unique to eukaryotes. We have identified 67 B-ZIP proteins in the Arabidopsis thaliana genome. No A.thaliana B-ZIP domains are homologous with any Homo sapiens B-ZIP domains. Here, we predict the dimerization specificity properties of the 67 B-ZIP proteins in the A.thaliana genome based on three structural properties of the dimeric alpha-helical leucine zipper coiled coil structure: (i) length of the leucine zipper, (ii) placement of asparagine or a charged amino acid in the hydrophobic interface and (iii) presence of interhelical electrostatic interactions. Many A.thaliana B-ZIP leucine zippers are predicted to be eight or more heptads in length, in contrast to the four or five heptads typically found in H.sapiens, a prediction experimentally verified by circular dichroism analysis. Asparagine in the a position of the coiled coil is typically observed in the second heptad in H.sapiens. In A.thaliana, asparagine is abundant in the a position of both the second and fifth heptads. The particular placement of asparagine in the a position helps define 14 families of homodimerizing B-ZIP proteins in A.thaliana, in contrast to the six families found in H.sapiens. The repulsive interhelical electrostatic interactions that are used to specify heterodimerizing B-ZIP proteins in H.sapiens are not present in A.thaliana. Instead, we predict that plant leucine zippers rely on charged amino acids in the a position to drive heterodimerization. It appears that A.thaliana define many families of homodimerizing B-ZIP proteins by having long leucine zippers with asparagine judiciously placed in the a position of different heptads.     

Genome relationship among nine species of Millettieae (Leguminosae: Papilionoideae) based on random amplified polymorphic DNA (RAPD)

Random amplified polymorphic DNA (RAPD) marker was used to establish intergeneric classification and phylogeny of the tribe Millettieae sensu Geesink (1984) (Leguminosae: Papilionoideae) and to assess genetic relationship between 9 constituent species belonging to 5 traditionally recognized genera under the tribe. DNA from pooled leaf samples was isolated and RAPD analysis performed using 25 decamer primers. The genetic similarities were derived from the dendrogram constructed by the pooled RAPD data using a similarity index, which supported clear grouping of species under their respective genera, inter- and intra-generic classification and phylogeny and also merger of Pongamia with Millettia. Elevation of Tephrosia purpurea var. pumila to the rank of a species (T. pumila) based on morphological characteristics is also supported through this study of molecular markers.     

Relationships among Doppler-derived umbilical artery absolute velocities, cardiac function, and placental volume blood flow and resistance in fetal sheep

We hypothesized that umbilical artery (UA) absolute blood flow velocities measured by Doppler ultrasonography reflect placental volume blood flow (Q(UA)) and placental vascular resistance (R(UA)) in a late gestation fetal sheep model. In addition, we examined the relationships between umbilical artery absolute blood flow velocities and parameters of fetal cardiac function. Twenty-six sheep fetuses were instrumented at 112-132 days of gestation. After a 5-day recovery period, experiments were performed under general anesthesia in 16 normal fetuses, in 5 fetuses after maternal administration of phenylephrine, and in 5 fetuses after placental embolization. The Q(UA) and arterial blood pressures were measured using a transit-time ultrasonic flow probe and a catheter placed into the descending aorta, respectively. UA peak systolic velocity (PSV), end-diastolic velocity (EDV), time-averaged maximum velocity (TAMXV), pulsatility index (PI), mean velocity (V(mean)), fetal cardiac output, ventricular ejection forces, and the proportion of isovolumetric relaxation time (IRT%) in the cardiac cycle were measured with the use of Doppler ultrasonography. Significant positive linear correlations were found between UA EDV, TAMXV, and V(mean) versus Q(UA), whereas UA PI had a significant negative correlation with Q(UA). Significant negative correlations were shown between UA EDV, TAMXV, and V(mean) versus R(UA). A significant positive correlation was present between UA PI and R(UA). Doppler-derived UA parameters did not correlate with fetal arterial blood pressures, cardiac output, ventricular ejection forces or IRT%. In fetal sheep, Doppler-derived UA PI and absolute velocities, except PSV, are closely related to directly measured Q(UA) and R(UA), validating the use of noninvasive Doppler velocimetry in the assessment of placental circulation.     

Nonlinear analysis of EEG signals at different mental states

Background  

The EEG (Electroencephalogram) is a representative signal containing information about the condition of the brain. The shape of the wave may contain useful information about the state of the brain. However, the human observer can not directly monitor these subtle details. Besides, since bio-signals are highly subjective, the symptoms may appear at random in the time scale. Therefore, the EEG signal parameters, extracted and analyzed using computers, are highly useful in diagnostics. This work discusses the effect on the EEG signal due to music and reflexological stimulation.     

Simultaneous storage of medical images in the spatial and frequency domain: A comparative study

Background  

Digital watermarking is a technique of hiding specific identification data for copyright authentication. This technique is adapted here for interleaving patient information with medical images, to reduce storage and transmission overheads.     

Humoral defence factors in Indian river prawn, Macrobrachium malcolmsonii

A preliminary study on humoral defence factors of Indian river prawn, Macrobrachium malcolmsonii was carried out. The serum of animals collected from intermoult stage had an average total protein content of 9.65 g dl(-1) and lysozyme-like activity of 0.04 unit ml(-1). The phenoloxidase activity in haemocyte lysate supernatant was triggered significantly (P < 0.05) by chitosan, Gram-positive and Gram-negative bacterial cells in comparison to other elicitors viz., levamisole, trypsin and glucan. The serum contained an agglutinin against Gram-negative bacteria and a haemagglutinin against a wide range of vertebrate erythrocytes. The haemagglutinin was stable over a wide range of pH (3.0-7.0) and temperatures (-30 degrees C to 60 degrees C). A 413 kDa N-acetyl galactosamine-specific haemagglutinin was purified by single step affinity chromatography and the protein was found to be calcium ion-dependent in nature and made up of five different subunits of varied molecular weights on denaturing SDS-PAGE.     

Structure of Mycobacterium tuberculosis single-stranded DNA-binding protein. Variability in quaternary structure and its implications

Single-stranded DNA-binding protein (SSB) is an essential protein necessary for the functioning of the DNA replication, repair and recombination machineries. Here we report the structure of the DNA-binding domain of Mycobacterium tuberculosis SSB (MtuSSB) in four different crystals distributed in two forms. The structure of one of the forms was solved by a combination of isomorphous replacement and anomalous scattering. This structure was used to determine the structure of the other form by molecular replacement. The polypeptide chain in the structure exhibits the oligonucleotide binding fold. The globular core of the molecule in different subunits in the two forms and those in Escherichia coli SSB (EcoSSB) and human mitochondrial SSB (HMtSSB) have similar structure, although the three loops exhibit considerable structural variation. However, the tetrameric MtuSSB has an as yet unobserved quaternary association. This quaternary structure with a unique dimeric interface lends the oligomeric protein greater stability, which may be of significance to the functioning of the protein under conditions of stress. Also, as a result of the variation in the quaternary structure the path adopted by the DNA to wrap around MtuSSB is expected to be different from that of EcoSSB.     

Role of conserved residues in structure and stability: tryptophans of human serum retinol-binding protein, a model for the lipocalin superfamily

Serum retinol binding protein (RBP) is a member of the lipocalin family, proteins with up-and-down beta-barrel folds, low levels of sequence identity, and diverse functions. Although tryptophan 24 of RBP is highly conserved among lipocalins, it does not play a direct role in activity. To determine if Trp24 and other conserved residues have roles in stability and/or folding, we investigated the effects of conservative substitutions for the four tryptophans and some adjacent residues on the structure, stability, and spectroscopic properties of apo-RBP. Crystal structures of recombinant human apo-RBP and of a mutant with substitutions for tryptophans 67 and 91 at 1.7 A and 2.0 A resolution, respectively, as well as stability measurements, indicate that these relatively exposed tryptophans have little influence on structure or stability. Although Trp105 is largely buried in the wall of the beta-barrel, it can be replaced with minor effects on stability to thermal and chemical unfolding. In contrast, substitutions of three different amino acids for Trp24 or replacement of Arg139, a conserved residue that interacts with Trp24, lead to similar large losses in stability and lower yields of native protein generated by in vitro folding. The results and the coordinated nature of natural substitutions at these sites support the idea that conserved residues in functionally divergent homologs have roles in stabilizing the native relative to misfolded structures. They also establish conditions for studies of the kinetics of folding and unfolding by identifying spectroscopic signals for monitoring the formation of different substructures.     

Sublethal temperature stress in juvenile Labeo rohita (Ham-Buch.) and Rita rita (Ham.): some physiological changes

Juveniles of fish L. rohita and R. rita subjected to a rapid (5 min) sublethal temperature increase from 28 to 35 degrees C showed significant increase in cortisol and decrease in interrenal ascorbic acid. Hypercholesterolemia, hyperglycemia and hyperlactemia were also evident accompanied by increased blood haemoglobin and haematocrit and stable protein levels. Compensatory responses were initiated within 72 hr in both the fishes. R. rita recovered more quickly indicating it to be more resistant to the heat stress than L. rohita. Hence fishes subjected to sublethal temperature stress should be given a metabolic recovery period of 72 hr prior to further stress being applied.