Synthesis of perbromates

Salts of heptavalent bromine were synthesized by a hot atom process, the beta decay of radioactive selenium-83 incorporated into a selenate. Formation of an unreactive perbromate ion led to preparation of macro amounts of perborate. A rubidium salt was isolated

Origin of Organic Matter in Early Solar System. I - Hydrocarbons

Formation of hydrocarbons by Fischer-Tropsch reaction involving carbon monoxide, hydrogen, and meteorite

Natural urine concentrations and composition in neotropical bats

1. 1. Among neotropical bats with subdivided renal medullae, some natural urine samples are equal in concentration to mean maximum calculated levels.2. 2. Natural urine osmotic pressures in frugivorous phyllostomids are less than in other phyllostomids which, in turn, are less than in insectivorous bats.3. 3. Urinary sodium (Na+) concentrations show no difference between frugivorous. insectivorous, and others, but urinary potassium (K+) levels in frugivores are higher than in other bats.4. 4. Natural urine concentrations are primarily related to diet and secondarily to environmental dehydration pressure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25423/1/0000872.pd

Effects of captivity on thermoregulation and metabolism in Artibeus jamaicensis (chiroptera: phyllostomatidae)

1. 1. In the Jamaican fig-eating bat, Artibeus jamaicensis, oxygen consumption (OC in cm3/g per hr) and deep body temperature (Tb in [deg]C) are significantly related to ambient temperature (Ta in [deg]C) and length of time in captivity, but not to the direction (low to high or high to low) of Ta change.2. 2. OC and Tb levels as functions of Ta rapidly change from those characteristic of a non-homeothermic endotherm on the day of capture to values characteristic of a homeothermic endotherm within 3-6 days in captivity.3. 3. Jamaican fig-eating bats examined within 12 hr of capture were physiologically distinct from individuals of this species kept briefly (3 days) in captivity.4. 4. Bats tested within 12 hr of capture at Tas of 30 and 25[deg]C required 1/3 and 2/3 less metabolic energy, respectively, than bats maintained briefly in captivity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23721/1/0000693.pd

Proximate, caloric, nitrogen and mineral composition of bodies of some tropical bats

Proximate (live mass, water, lipid, ash, non-fat organic), caloric, nitrogen, and mineral (sodium, potassium, calcium, magnesium, and iron) concentrations and total body content of individuals of 24 species of Neotropical and Paleotropical bats were determined. Mass-related, concentration patterns were found for all measured variables, except iron. Concentrations increase with size for nitrogen, calcium, and magnesium but are concave, opening upward, for sodium and potassium. These last two elements reach minimal concentrations in bats weighing about 22 and 28 g dry mass, respectively. Total body content of nitrogen and minerals was compared with amounts in similar-sized birds and tetrapodal mammals.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31225/1/0000127.pd

Analysis of polynomial functions for determining maximum or minimum conditions in biological systems

1. When physiological condition is curvilinearly related to environmental conditions, the "optimum" environmental condition is frequently determined by intersecting two straight lines.2. Errors in this method are discussed, and a more precise method is suggested.3. The curvilinear function is described by polynomial regression.4. Optimum values of the independent variable (i.e. those resulting in maximum or minimum physiological responses) are found where the slope is zero, and can be calculated easily from the first derivative of the regression line.5. Two examples are given: heart rate-temperature and oxygen consumption-pH.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22151/1/0000582.pd

Bioenergetics in two pulmonate snails, Helisoma and Physa

Energy budgets constructed for the pulmonate snails, Physa gyrina and Helisoma trivolvis, indicate:Abstract1. 1. Assimilation efficiency in wild type Physa (88[middle dot]9 per cent) and Helisoma (73[middle dot]2 per cent) are exceptionally high when compared to reported values for invertebrates while assimilation efficiency in an albino strain of Helisoma, although above average for most invertebrates, is comparatively low (59[middle dot]8 per cent).2. 2. With a single exception, there are no relationships between weight or weight gain and food (energy) ingested, wastes (energy) egested, assimilation efficiency or energy devoted to reproduction.3. 3. Daily food energy ingested by wild P. gyrina (27[middle dot]5 cal/day) and H. trivolvis (27[middle dot]6 cal/day) are similar and significantly higher than daily food energy ingested by albino H. trivolvis (15[middle dot]9 cal/day).4. 4. Albino H. trivolvis devoted more energy to egg production (2[middle dot]1 cal/day) than did the wild variety (1[middle dot]1 cal/day).5. 5. Secondary productivity of both varieties of H. trivolvis were exceptionally high (17[middle dot]8 and 32[middle dot]6 per cent).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22019/1/0000435.pd

A Revised Design for Microarray Experiments to Account for Experimental Noise and Uncertainty of Probe Response

Background Although microarrays are analysis tools in biomedical research, they are known to yield noisy output that usually requires experimental confirmation. To tackle this problem, many studies have developed rules for optimizing probe design and devised complex statistical tools to analyze the output. However, less emphasis has been placed on systematically identifying the noise component as part of the experimental procedure. One source of noise is the variance in probe binding, which can be assessed by replicating array probes. The second source is poor probe performance, which can be assessed by calibrating the array based on a dilution series of target molecules. Using model experiments for copy number variation and gene expression measurements, we investigate here a revised design for microarray experiments that addresses both of these sources of variance. Results Two custom arrays were used to evaluate the revised design: one based on 25 mer probes from an Affymetrix design and the other based on 60 mer probes from an Agilent design. To assess experimental variance in probe binding, all probes were replicated ten times. To assess probe performance, the probes were calibrated using a dilution series of target molecules and the signal response was fitted to an adsorption model. We found that significant variance of the signal could be controlled by averaging across probes and removing probes that are nonresponsive or poorly responsive in the calibration experiment. Taking this into account, one can obtain a more reliable signal with the added option of obtaining absolute rather than relative measurements. Conclusion The assessment of technical variance within the experiments, combined with the calibration of probes allows to remove poorly responding probes and yields more reliable signals for the remaining ones. Once an array is properly calibrated, absolute quantification of signals becomes straight forward, alleviating the need for normalization and reference hybridizations

A two-domain elevator mechanism for sodium/proton antiport

Sodium/proton (Na+/H+) antiporters, located at the plasma membrane in every cell, are vital for cell homeostasis1. In humans, their dysfunction has been linked to diseases, such as hypertension, heart failure and epilepsy, and they are well-established drug targets2. The best understood model system for Na+/H+ antiport is NhaA from Escherichia coli1, 3, for which both electron microscopy and crystal structures are available4, 5, 6. NhaA is made up of two distinct domains: a core domain and a dimerization domain. In the NhaA crystal structure a cavity is located between the two domains, providing access to the ion-binding site from the inward-facing surface of the protein1, 4. Like many Na+/H+ antiporters, the activity of NhaA is regulated by pH, only becoming active above pH 6.5, at which point a conformational change is thought to occur7. The only reported NhaA crystal structure so far is of the low pH inactivated form4. Here we describe the active-state structure of a Na+/H+ antiporter, NapA from Thermus thermophilus, at 3 Å resolution, solved from crystals grown at pH 7.8. In the NapA structure, the core and dimerization domains are in different positions to those seen in NhaA, and a negatively charged cavity has now opened to the outside. The extracellular cavity allows access to a strictly conserved aspartate residue thought to coordinate ion binding1, 8, 9 directly, a role supported here by molecular dynamics simulations. To alternate access to this ion-binding site, however, requires a surprisingly large rotation of the core domain, some 20° against the dimerization interface. We conclude that despite their fast transport rates of up to 1,500 ions per second3, Na+/H+ antiporters operate by a two-domain rocking bundle model, revealing themes relevant to secondary-active transporters in general

Cold-adapted RTX lipase from antarctic Pseudomonas sp. strain AMS8: isolation, molecular modeling and heterologous expression

A new strain of psychrophilic bacteria (designated strain AMS8) from Antarctic soil was screened for extracellular lipolytic activity and further analyzed using molecular approach. Analysis of 16S rDNA showed that strain AMS8 was similar to Pseudomonas sp. A lipase gene named lipAMS8 was successfully isolated from strain AMS8, cloned, sequenced and overexpressed in Escherichia coli. Sequence analysis revealed that lipAMS8 consist of 1,431 bp nucleotides that encoded a polypeptide consisting of 476 amino acids. It lacked an N-terminal signal peptide and contained a glycine- and aspartate-rich nonapeptide sequence at the C-terminus, which are known to be the characteristics of repeats-in-toxin bacterial lipases. Furthermore, the substrate binding site of lipAMS8 was identified as S207, D 255 and H313, based on homology modeling and multiple sequence alignment. Crude lipase exhibited maximum activity at 20 C and retained almost 50 % of its activity at 10 C. The molecular weight of lipAMS8 was estimated to be 50 kDa via sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The optimal expression level was attained using the recombinant plasmid pET32b/BL21(DE3) expressed at 15 C for 8 h, induced by 0.1 mM isopropyl β-D thiogalactoside (IPTG) at E. coli growth optimal density of 0.5