Catalysis of decarboxylation by a preorganized heterogeneous microenvironment: crystal structures of abzyme 21D8

Antibody 21D8 catalyzes the solvent-sensitive decarboxylation of 3-carboxybenzisoxazoles. The crystal structure of chimeric Fab 21D8 with and without hapten at 1.61 A and 2.10 A, respectively, together with computational analysis, shows how a melange of polar and non-polar sites are exploited to achieve both substrate binding and acceleration of a reaction normally facilitated by purely aprotic dipolar media. The striking similarity of the decarboxylase and a series of unrelated esterase antibodies also highlights the chemical versatility of structurally conserved anion binding sites and the relatively subtle changes involved in fine-tuning the immunoglobulin pocket for recognition of different ligands and catalysis of different reactions.     

Localisation of the Vacuolar Proton Pump (V-H+-ATPase) and Carbonic Anhydrase II in the Human Eccrine Sweat Gland

The localisation of the vacuolar proton pump (V-H+ -ATPase) and the enzyme carbonic anhydrase II (CAII) was investigated in the human eccrine sweat gland employing standard immunohistochemical techniques after antigen retrieval using microwave heat treatment and high pressure. The high-pressure antigen retrieval unmasked the presence of V-H+ -ATPase in the clear cells of the secretory coil, with a distribution similar to that previously observed for CAII. However, the dark cells were unreactive to both antibodies. In addition, heat and high-pressure antigen retrieval demonstrated the presence of CAII in the apical zone of luminal cells of the reabsorptive duct, a location not previously reported. The localisation of V-H+ -ATPase and CAII in the secretory coil clear cells suggests that the formation of HCO3- and H+ by carbonic anhydrase II and the transport of H+ by V-H+ -ATPase may play an role in sweat fluid secretion. Their presence at the apex of the duct cells indicates involvement in ductal ion reabsorption.     

Measurement of trace elements in proteins extracted from liver by size exclusion chromatography-inductively coupled plasma-mass spectrometry with a magnetic sector mass spectrometer

Proteins are extracted from liver into aqueous buffer at pH 7 and separated by size exclusion chromatography (SEC). Inductively coupled plasma mass spectrometry (ICP-MS) with a magnetic sector mass spectrometer is used to identify those protein fractions that contain Cu, Zn, Mn, Fe, Cd, S, P, Mo, Co, Ca, or Mg. The experimental setup provides very high sensitivity. Measurements at medium spectral resolution remove polyatomic interferences for some difficult elements like Fe, S, and P. Some elements are found in different molecular weight proteins; for example, cadmium binds to four different protein fractions (>400 kDa, 70 kDa, and metallothionein). Other elements like Mo, Ca, and Mg are present only in low-molecular-weight proteins or other small molecules.     

Aromaticity and Antiaromaticity in Small Ring Transition States, Assessed by NICS Values and Energetics

Nucleus Independent Chemical Shift (NICS) values, pioneered by Schleyer, provide detailed insights into electronic structures of transition states. These show that the [2+2+2]-cycloaddition transition states, studied early by Schleyer and by us, have aromatic transition structures and that fused cyclopropanes are aromatic in the transition structure, while fused four-membered rings are antiaromatic. The nucleophilic ring-opening of 1- and 2-cyanobicyclo[1.1.0]butanes, studied earlier by Hoz, and ring openings of cyanocyclopropane, cyanocyclobutane, and 2-cyanobicyclo[2.2.0]hexane by hydroxide were investigated at the B3LYP/6-31+G* level. Orbital interactions through bonds explain relative facilities of ring opening.Electronic Supplementary Material available.     

Electrophoretic characterization of the nonspecific esterases of the mosquito, Culex tarsalis: conventional and isoelectric focused acrylamide gels.

1. The nonspecific esterases of the mosquito, Culex tarsalis, were examined through conventional and isoelectric focusing acrylamide gel electrophoresis. 2. Conventional acrylamide gel electrophoresis resolved five components. These were characterized as: three carboxylesterases, one acetylcholinesterase and one acetylesterase. 3. Isoelectric focusing resolved 18 components. These were characterized as: 14 carboxylesterases, two acetylcholinesterases, one acetylesterase and one arylesterase. 4. The reproducibility and reliability of isoelectric focusing is discussed and compared to conventional acrylamide gel electrophoresis for the examination of multi-component isozyme systems such as non-specific esterases.     

Control strategies in physiological systems

In this paper, written for a general audience, I review and contrast various strategies that the body uses to control homeostasis and movement. Messages, signals, communication channels, and control systems are dealt with from both a cellular and an integrative perspective. The major global control strategies are feedback, feedforward, and adaptive control, and examples of each are presented to highlight advantageous and disadvantageous features. Many physiological systems use these three strategies in combination.     

Trait structure and redundancy determine sensitivity to disturbance in marine fish communities

Trait diversity is believed to influence ecosystem dynamics through links between organismal traits and ecosystem processes. Theory predicts that key traits and high trait redundancy—large species richness and abundance supporting the same traits—can buffer communities against environmental disturbances. While experiments and data from simple ecological systems lend support, large‐scale evidence from diverse, natural systems under major disturbance is lacking. Here, using long‐term data from both temperate (English Channel) and tropical (Seychelles Islands) fishes, we show that sensitivity to disturbance depends on communities’ initial trait structure and initial trait redundancy. In both ecosystems, we found that increasing dominance by climatically vulnerable traits (e.g., small, fast‐growing pelagics/corallivores) rendered fish communities more sensitive to environmental change, while communities with higher trait redundancy were more resistant. To our knowledge, this is the first study demonstrating the influence of trait structure and redundancy on community sensitivity over large temporal and spatial scales in natural systems. Our results exemplify a consistent link between biological structure and community sensitivity that may be transferable across ecosystems and taxa and could help anticipate future disturbance impacts on biodiversity and ecosystem functioning.