Thermal damage to chloroplast envelope membranes

Nuclear magnetic resonance was used to detect thermal injury to chloroplasts in vivo. A lesion occurs in the chloroplast envelope membrane at temperatures between 53°C and 57°C, depending on species, leaf condition, and heating rate. The injury is associated with a sudden loss of water from the chloroplast.     

Water is allocated differently to chloroplasts in sun and shade leaves

Hydrogen-1 nuclear magnetic resonance spectroscopy was used to study water allocation in cell compartments of sun and shade leaves. NMR spectra of Acer platanoides were resolved into two peaks that were assigned to chloroplast and nonchloroplast water. Sun leaves contained 1.7 times more water per unit area of surface than shade leaves, and the water was allocated differently. Chloroplasts in sun leaves contained 17% of the total leaf water versus 47% in shade leaves. Comparing equal leaf surface areas, the chloroplasts in shade leaves contained 60% more water than those in sun leaves.     

Correlation proton magnetic resonance studies at 250 MHz of bovine pancreatic ribonuclease. I. Reinvestigation of the histidine peak assignments.

The deuterium exchange kinetics of the C(2) protons of the four histidine residues of native bovine pancreatic ribonuclease A have been followed at pH 6.5 and 8.0 by proton magnetic resonance spectroscopy (1H NMR). Comparison of the order of exchange of the histidine peaks with tritium exchange rates into individual histidine residues [Ohe, M., Matsuo, H., Sakiyama, F., and Narita, K. (1974), J. Biochem. (Tokyo) 75, 1197] supports the previous assignment of histidine NMR peaks H(1) and H(4) to histidine-105 and histidine-48 but requires reassignment of peaks H(2) and H(3) to histidine-119 and histidine-12, respectively. Ribonuclease A samples having differentially deuterated histidines have been used to verify the existence of crossover points in the histidine proton magnetic resonance titration curves and to observe the discontinuous titration curve of histidine-48. Proton magnetic resonance peaks have been assigned to the C(4) protons of the four histidine residues of ribonuclease A on the basis of their unit proton areas and by matching their titration shifts with the more readily visible C(2)-H peaks of the histidines. The pK' values derived from the C(4)-H data agree, within experimental limits, with those derived from C(2)-H data. The C(4)-H peaks were assigned to histidine-12, -48, -105, and -119 of ribonuclease A on the basis of their pH dependence, pK' values, shifts of their pK' values in the presence of inhibitor cytidine 3'-phosphate, and by comparison with the assignments of the histidine C(2)-H peaks above.     

Bone marrow suppression and severe anaemia associated with persistent Plasmodium falciparum infection in African children with microscopically undetectable parasitaemia

In sub-Saharan Africa the highest overlap between malaria and HIV infections occurs in female adolescents. Yet control activities for these infections are directed to different target groups, using disparate channels. This reflects the lack of priority given to adolescents and the absence of an accepted framework for delivering health and health-related interventions to this high-risk group. In this paper it is argued that female adolescents require a continuum of care for malaria and HIV – prior to conception, during and after pregnancy and that this should be provided through adolescent services. The evidence for this conclusion is presented. A number of African countries are commencing to formulate and implement adolescent-friendly policies and services and disease control programs for malaria and HIV will need to locate their interventions within such programs to ensure widespread coverage of this important target group. Failure to prioritize adolescent health in this way will seriously limit the success of disease control programs for malaria and HIV prevention.     

One- and two-dimensional NMR spectral analysis of the consequences of single amino acid replacements in proteins

The traditional approach of using homologous sequences to elucidate the role of specific amino acid residues in protein structure and function becomes more meaningful as the number of differences is minimized, with the limit being alteration of a single residue. For small proteins in solution, NMR spectroscopy offers a means of obtaining detailed information about each residue and its response to a given change in the protein sequence. Extraction of this information has been aided by recent progress in spectrometer technology (higher magnetic fields, more sensitive signal detection, more sophisticated computers) and experimental strategies (new NMR pulse sequences including multiple-quantum and two-dimensional NMR methods). The set of avian ovomucoid third domains, which consists of the third domain proper plus a short leader (connecting peptide) and has a maximum of 56 amino acid residues, offers an attractive system for developing experimental methods for investigating sequence-structure and structure-function relationships in proteins. Our NMR results provide examples of sequence effects on pKa' values, average conformation, and internal motion of amino acid side chains.     

Caloric Restriction Engages Hepatic RNA Processing Mechanisms in Rhesus Monkeys

1. Download high-res image (305KB)
2. Download full-size image

     

Caranday—A source of palm wax

Millions of these palm trees in the Gran Chaco of central South America, occupying parts of Argentina, Bolivia and Paraguay, offer an unexploited commercial source of a hard vegetable wax, potentially as great as that of carnauba palm in northeastern Brazil.     

Addressing the intrinsic disorder bottleneck in structural proteomics

The Center for Eukaryotic Structural Genomics (CESG), as part of the Protein Structure Initiative (PSI), has established a high-throughput structure determination pipeline focused on eukaryotic proteins. NMR spectroscopy is an integral part of this pipeline, both as a method for structure determinations and as a means for screening proteins for stable structure. Because computational approaches have estimated that many eukaryotic proteins are highly disordered, about 1 year into the project, CESG began to use an algorithm (the Predictor of Naturally Disordered Regions, PONDR to avoid proteins that were likely to be disordered. We report a retrospective analysis of the effect of this filtering on the yield of viable structure determination candidates. In addition, we have used our current database of results on 70 protein targets from Arabidopsis thaliana and 1 from Caenorhabditis elegans, which were labeled uniformly with nitrogen-15 and screened for disorder by NMR spectroscopy, to compare the original algorithm with 13 other approaches for predicting disorder from sequence. Our study indicates that the efficiency of structural proteomics of eukaryotes can be improved significantly by removing targets predicted to be disordered by an algorithm chosen to provide optimal performance.