Solid-phase oligosaccharide synthesis and related technologies

Research efforts directed at the development of methodologies effective for solid-phase synthesis of oligosaccharides have resulted in a number of impressive achievements. In addition, closely related technologies, such as soluble polymer-supported synthesis and fluorous synthesis of the same class of molecules, have proved to be quite promising.     

Lipid polymorphism and biomembrane function

In recent years, several major developments have taken place in the biology, physical chemistry and technology of polymorphism of membrane lipids. These include the identification of polymorphic regulation of membrane lipid composition in Escherichia coli, the importance of nonbilayer lipids for protein functioning, the special packing properties of bilayers containing these lipids, and the crystalization of a membrane protein out of three dimensional bilayer networks (lipid cubic phases). These exciting developments bring us closer to understanding the paradox of the lipid bilayer structure of biomembranes and the molecular basis of membrane protein structure and function.     

Phospholipid membrane bending as assessed by the shape sequence of giant oblate phospholipid vesicles

Vesicle shape transformations caused by decreasing the difference between the equilibrium areas of membrane monolayers were studied on phospholipid vesicles with small volume to membrane area ratios. Slow transformations of the vesicle shape were induced by lowering of the concentration of lipid monomers in the solution outside the vesicle. The complete sequence of shapes consisted of a string of pearls, and wormlike, starfish, discocyte and stomatocyte shapes. The transformation from discocyte to stomatocyte vesicle shapes was analyzed theoretically to see whether these observations accord with the area difference elasticity (ADE) model. The membrane shape equation and boundary conditions were derived for axisymmetrical shapes for low volume vesicles, part of whose membranes are in contact. Calculated shapes were arranged into a phase diagram. The theory predicts that the transition between discocyte and stomatocyte shapes is discontinuous for relatively high volumes and continuous for low volumes. The calculated shape sequences matched well with the observed ones. By assuming a linear decrease of the equilibrium area difference with time, the ratio between the nonlocal and local bending constants is in agreement with reported values.     

The mechanism and control of cytokinesis

Cytokinesis is under active investigation in each of the dominant experimental model systems. During 1996 and 1997, several developments necessitated the reassessment of the prevailing model for cytokinesis. In addition, the inventory of proteins required for cytokinesis has grown considerably. However, a molecular understanding of cytokinesis still remains elusive.     

Insights into the mechanisms of homologous recombination from the structure of RuvA

The recent structure determination of RuvA has provided the first insights into the structural basis for its interaction with Holliday junction DNA. Multiple copies of a helix-hairpin-helix motif which line the four grooves between the monomers in the tetrameric structure are thought to be involved in the interaction of the protein with its DNA target. This suggests that the four arms of the junction are held by RuvA in a fourfold symmetric arrangement and has fuelled ideas on the way in which components of the Ruv complex combine to catalyse the process of homologous recombination     

Human evolution and the mitochondrial genome

The use of mitochondrial DNA (mtDNA) continues to dominate studies of human genetic variation and evolution. Recent work has re-affirmed the strict maternal inheritance of mtDNA, yielded new insights into the extent and nature of intra-individual variation, supported a recent African origin of human mtDNA, and amply demonstrated the utility of mtDNA in tracing population history and in analyses of ancient remains.     

Structure and dynamics of green fluorescent protein

Many marine organisms are luminescent. The proteins that produce the light include a primary light producer (aequorin or luciferase) and often a secondary photoprotein that red shifts the light for better penetration in the ocean. Green fluorescent protein is one such secondary protein. It is remarkable in that it autocatalyzes the formation of its own fluorophore and thus can be expressed in variety of organisms in its fluorescent form. The recent determination of its 3D structure and other physical characterizations are revealing its molecular mechanism of action     

Ionic currents, transmitters and models of motor pattern generators

Recent work, combining direct study of ion channels and synapses with pharmacological manipulations and realistic computer simulations, has deepened our understanding of how motor circuits produce rhythmic outputs. In several preparations, both the roles of some key ionic currents in circuit operation and the mechanisms by which circuit operation may be modulated have been identified.     

The chemical-biological interface: developments in automated and miniaturised screening technology

The rapidly changing developments in genomics and combinatorial chemistry, generating new drug targets and large numbers of compounds, have caused a revolution in high-throughput screening technologies. Key to this revolution has been the introduction of robotics and automation, together with new biological assay technologies (e.g., homogeneous time resolved fluorescence). With ever increasing workloads, together with economic and logistical constraints, miniaturisation is rapidly becoming essential for the future of high-throughput screening and combinatorial chemistry. This is evident from the introduction of high-density microtitre plates, small volume liquid handling robots and associated detection technology.     

On growth and form: control of cell morphogenesis in fission yeast

In the past year, we have gained considerable insight into the process of cell morphogenesis and the establishment of positional information in fission yeast. The highlights include a better understanding of the role of the microtubule cytoskeleton in the control of cell shape, as well as the identification of novel genes essential for the establishment of cell polarity and for the positioning of the site of cell division.     

Biorobotic approaches to the study of motor systems

Biorobotics is a promising new area of research at the interface between biology and robotics. Robots can either be used as physical models of biological systems or be directly inspired by biological studies. A great deal of progress has recently been made in biorobotic studies of locomotion, orientation, and vertebrate arm control.     

Nucleotide Sequence, Genomic Organization, and Chromosomal Localization of Genes Encoding the Human NMDA Receptor Subunits NR3A and NR3B

The N-methyl-D-aspartate (NMDA) receptors are glutamate-regulated ion channels that are critically involved in important physiological and pathological functions of the mammalian central nervous system. We have identified and characterized the gene encoding the human NMDA receptor subunit NR3A (GRIN3A), as well as the gene (GRIN3B) encoding an entirely novel subunit that we named NR3B, as it is most closely related to NR3A (57.4% identity). GRIN3A localizes to chromosome 9q34, in the region 13-34, and consists of nine coding exons. The deduced protein contains 1115 amino acids and shows 92.7% identity to rat NR3A. GRIN3B localizes to chromosome 19p13.3 and contains, as does the mouse NR3B gene (Grin3b), eight coding exons. The deduced proteins of human and mouse NR3B contain 901 and 900 amino acid residues, respectively (81.6% identity). In situ hybridization shows a widespread distribution of Grin3b mRNA in the brain of the adult rat.     

Enzyme models: design and selection

There are two approaches to the discovery of enzyme mimics, that is identifying molecules that are able to bind substrate(s) and then catalyze reactions. The first approach, often inspired by enzymes themselves, utilises chemical knowledge and experience to design the catalyst. The other approach is to create a library and select the best host of a transition state analogue of the required reaction.     

Novel cofactor derivatives and cofactor-based models

In 1997 and the first half of 1998, numerous publications appeared reporting studies of cofactors and their analogues in classical model systems and in enzyme-catalyzed reactions directed at understanding the enzymatic reactions of their natural cofactors. Model systems based on flavins have provided new insights into enzymatic modulation of the flavin reduction potential, and enzymatic reactions of coenzyme A analogues and derivatives have been employed in several studies of coenzyme A utilizing enzymes. Coenzyme B₁₂ analogues have been utilized as alternate cofactors for B₁₂-utilizing enzymes, while pyrroloquinoline quinone esters and analogues have been employed in model studies of the reactions of quinoprotein-catalyzed reactions.