In general, proteins fold with hydrophobic residues buried, away from water. Reversible protein folding due to hydrophobic interactions results from inverse temperature transitions where folding occurs on raising the temperature. Because homoiothermic animals constitute an infinite heat reservoir, it is the transition temperature, Tt, not the endothermic heat of the transition, that determines the hydrophobically folded state of polypeptides at body temperature. Reported here is a new hydrophobicity scale based on the values of Tt for each amino acid residue as a guest in a natural repeating peptide sequence, the high polymers of which exhibit reversible inverse temperature transitions. Significantly, a number of ways have been demonstrated for changing Tt such that reversibly lowering Tt from above to below physiological temperature becomes a means of isothermally and reversibly driving hydrophobic folding. Accordingly, controlling Tt becomes a mechanism whereby proteins can be induced to carry out isothermal free energy transduction.

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The complete series of the recommended generic biological tests for materials and devices in contact with tissues and tissue fluids and blood have been carried out by an independent testing laboratory on the elastic protein-based (bioelastic) polymer, Poly(L-Val1-L-Pro2-Gly3-L-Val 4-Gly5) with a degree of polymerization greater than 120, and its 20 Mrad γ-irradiation cross linked elastic matrix, X20-poly(VPGVG). The specific tests and the summarized results given in parentheses are: (1) the Ames mutagenicity test (non- mutagenic), (2) cytotoxicity-agarose overlay (non-toxic), (3) acute systemic tox icity (non-toxic), (4) intracutaneous toxicity (non-toxic), (5) muscle implantation (favorable), (6) acute intraperitoneal toxicity (non-toxic), (7) systemic antigenic ity (non-antigenic), (8) dermal sensitization—the Magnusson and Kligman maximization method (non-sensitizing), (9) pyrogenicity (non-pyrogenic), (10) Lee White clotting study (normal clotting time), and (11) in vitro hemolysis test (non-hemolytic). Thus, this new elastomeric polypeptide biomaterial which is based on the most striking repeating sequence in the mammalian elastic fiber exhibits an extraordinary biocompatibility. This parent bioelastic material and a wide range of component peptide variations are under development for an equally wide range of potential medical applications such as prevention of adhesions, drug delivery, and synthetic arteries.

Hydrological connections between river channels and their adjacent floodplains facilitate the flux of organisms and nutrients and access to increased habitat and new resources. Hydrological connections also deliver water subsidy and potentially disturb (through hydraulic forces) floodplain ecosystems. This study investigates the role of hydrological connectivity as a driver of patterns in wetland plant assemblages in billabongs on the floodplain of an Australian dryland river, exploring indirectly the relative importance of the mechanisms of flux, subsidy and disturbance. Wetland plants were surveyed in billabongs across gradients of hydrological connectivity and depth. Surveys were accompanied by experiments examining germination from the soil seed banks of each site under submerged and waterlogged conditions. The patterns in extant and germinant plant communities in relation to connectivity and depth gradients were used to infer the relative importance of the connectivity-related mechanisms of flux, subsidy and hydraulic disturbance in structuring wetland plant communities. Depth influenced both extant and germinating plant communities. Shallow billabongs supported a greater diversity and abundance of plants, and greater numbers and diversity of germinable seeds in the seed bank. Germination of seeds was greater in waterlogged soils than submerged soils. Thus, the main controls of plant abundance in wetlands appear to be availability of waterlogged soil habitat for germination and absence of light limitation for growth. Hydrological connectivity did not influence the abundance of plants or germinable seeds, but did influence species presence-absence in growing vegetation; this effect did not extend to the germinating community. Thus, hydrological connection does not appear to influence wetland vegetation by facilitating the movement of propagules between habitats. Instead, the patterns observed are consistent with hydrological connection providing a cue for germination through the delivery of water, and by modifying hydraulic habitat.

SUMMARYNitrous oxide (N2O) misuse is widespread in the UK. Although it is well-known that it can cause devastating myeloneuropathy, psychiatric presentations are poorly described. There is little understanding of who it affects, how it presents, its mechanism of action and principles of treatment. We begin this article with a case study. We then review the literature to help psychiatrists understand this area and deal with this increasing problem, and make diagnosis and treatment recommendations. We describe a diagnostic pentad of weakness, numbness, paraesthesia, psychosis and cognitive impairment to alert clinicians to the need to urgently treat these patients. Nitrous oxide misuse is a pending neuropsychiatric emergency requiring urgent treatment with vitamin B12 to prevent potentially irreversible neurological and psychiatric symptoms.