Chemical complementation identifies a proton acceptor for redox-active tyrosine D in photosystem II

Through the use of site-directed mutagenesis and chemical rescue, we have identified the proton acceptor for redox-active tyrosine D in photosystem II (PSII). Effects of chemical rescue on the tyrosyl radical were monitored by EPR spectroscopy. We also have acquired the Fourier–transform infrared (FT-IR) spectrum associated with the oxidation of tyrosine D and concomitant protonation of the acceptor. Mutant and isotopically labeled PSII samples are used to assign vibrational lines in the 3,600–3,100 cm−1 region to N-H modes of His-189 in the D2 polypeptide. When His-189 in D2 is changed to a leucine (HL189D2) in PSII, dramatic alterations of both EPR and FT-IR spectra are observed. When imidazole is introduced into HL189D2 samples, results from both EPR and FT-IR spectroscopy argue that imidazole is functionally reconstituted into an accessible pocket and that imidazole acts as a chemical mimic for His-189. Small perturbations of EPR and FT-IR spectra are consistent with access to this pocket in wild-type PSII, as well. Structures of the analogous site in bacterial reaction centers suggest that an accessible pocket, large enough to contain imidazole, is bordered by tyrosine D and His-189 in the D2 polypeptide. These data provide evidence that His-189 in the D2 polypeptide of PSII acts as a proton acceptor for redox-active tyrosine D and that proton transfer to the imidazole ring facilitates the efficient oxidation/reduction of tyrosine D.

The catalytic and other residues essential for the activity of the midgut trehalase from Spodoptera frugiperda

Trehalase (EC 3.2.1.28) hydrolyzes only alpha, alpha`- trehalose and is present in a variety of organisms, but is most important in insects and fungi. Crystallographic data showed that bacterial trehalase has 0312 and E496 as the catalytical residues and three Arg residues in the active site. Those residues have homologous in all family 37 trehalases including Spodoptera frugiperda trehalase (0322, E520, R169, R227, R287). To test the role of these residues, mutants of trehalase were produced. All mutants were at least four orders of magnitude less active than wild type trehalase and no structural difference between these mutants and wild type enzyme were discernible by circular dichroism. D322A and E520 pH-activity profile lacked the alkaline arm and the acid arm, respectively, suggesting that D322 is the acid and E520 the basic catalyst. Azide increases E520A activity three times, confirming its action as the basic catalyst. Taking into account the decrease in activity after substitution for alanine residue, the three arginine residues are as important as the catalytical ones to trehalase activity. This clarifies the previous misidentification of an Arg residue as the acid catalyst. As far as we know, this is the first report on the functional identification residues important for trehalase activity. (C) 2010 Elsevier Ltd. All rights reserved.

Structure-Function Relations in the PI-PLC/GDPD Enzyme Superfamily

Phosphatidylinositol-specific phospholipases C (PI-PLC) are known to participate in many eukaryotic signal transduction pathways and act as virulence factors in lower organisms. Glycerophosphoryl diester phosphodiesterase (GDPD) enzymes are involved in phosphate homeostasis and phospholipid catabolism for energy production. Streptomyces antibioticus phosphatidylinositol-specific phospholipase C (SaPLC1) is a 38 kDa enzyme that displays characteristics of both enzyme superfamilies, representing an evolutionary link between these divergent enzyme classes. SaPLC1 also boasts a unique catalytic mechanism that involves a trans 1,6-cyclic inositol phosphate intermediate instead of the typical cis 1,2-cyclic inositol phosphate. The mechanism by which this occurs is still unclear. To attack this problem, we established a wide mutagenesis scan of the active site and measured activities of alanine mutants. A chemical rescue assay was developed to verify that the activity loss was due to the removal of the functional role of the mutated residue. 31P-NMR was employed in characterizing and quantifying intermediates in mutants that slowed the reaction sufficiently. We found that the H37A and H76A mutations support the hypothesis that these structurally conserved residues are also conserved in terms of their catalytic roles. H37 was found to be the general base (GB), while H76 plays the role of general acid (GA). K131 was identified as a semi-conserved key positive charge donor found at the entrance of the active site. By elucidating the SaPLC1 mechanism in relation to its active site architecture, we have increased our understanding of the structure-function relations that support catalysis in the PI-PLC/GDPD superfamily. These findings provide groundwork for in vivo studies of SaPLC1 function and its possible role in novel signaling or metabolism in Streptomyces.

Chemical composition of 169 sediment profiles from the Arctic seas

This data set contains chemical composition of bottom sediments collected by scientists from the V.P. Zenkovich Laboratory of Shelf and Sea Coasts (P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences) during the Project ''Arctic Shelf of the Eurasia in the Late Quaternary'' in a number of expeditions to the Barents, Kara, East Siberian and Chukchi Seas on board research vessels R/V Professor Shtokman, H/V Dmitry Laptev, H/V Malygin, and icebreaker Georgy Sedov between 1978 and 1990. The analyses have been carried out in the Analytical Laboratory of the P.P. Shirshov Institute of Oceanology. Archiving and electronic publication was performed through a data rescue by Evgeny Gurvich in 2003.

Sexual selection in a tropical fruit fly : role of a plant derived chemical in mate choice

The specific mechanisms by which selective pressures affect individuals are often difficult to resolve. In tephritid fruit flies, males respond strongly and positively to certain plant derived chemicals. Sexual selection by female choice has been hypothesized as the mechanism driving this behaviour in certain species, as females preferentially mate with males that have fed on these chemicals. This hypothesis is, to date, based on studies of only very few species and its generality is largely untested. We tested the hypothesis on different spatial scales (small cage and seminatural field-cage) using the monophagous fruit fly, Bactrocera cacuminata. This species is known to respond to methyl eugenol (ME), a chemical found in many plant species and one upon which previous studies have focused. Contrary to expectation, no obvious female choice was apparent in selecting ME-fed males over unfed males as measured by the number of matings achieved over time, copulation duration, or time of copulation initiation. However, the number of matings achieved by ME-fed males was significantly greater than unfed males 16 and 32 days after exposure to ME in small cages (but not in a field-cage). This delayed advantage suggests that ME may not influence the pheromone system of B. cacuminata but may have other consequences, acting on some other fitness consequence (e.g., enhancement of physiology or survival) of male exposure to these chemicals. We discuss the ecological and evolutionary implications of our findings to explore alternate hypotheses to explain the patterns of response of dacine fruit flies to specific plant-derived chemicals.

Assessing organizational culture? value management to the rescue

As part of a Doctor of Business Administration degree programme jointly run by Curtin University, Perth, Australia and Lingnan University, Hong Kong, a research thesis relating organizational effectiveness to the organizational culture of Hong Kong construction firms involved in public housing is being undertaken. Organizational effectiveness is measured by the Housing Department (HD) Performance Assessment Scoring System (PASS) and organizational culture traits and strengths have been measured by using the Denison Organizational Culture Survey (OCS), developed by Daniel Denison and William S. Neale and based on 16 years of research involving over 1,000 organizations. The PASS scores of building contractors are compared with the OCS scores to determine if there is any significant correlation between highly effective companies and particular organizational strengths and traits. Profiles are then drawn using the Denison Model and can be compared against ‘norms’ for the industry sector on which the survey has been carried out. The next stage of the work is to present the results of the survey to individual companies, conduct focus group interviews to test the results, discover more detail on that company’s culture and discuss possible actions based on the results. It is in this latter stage that certain value management techniques may well prove very useful.

Chemical functionalities of high and low sulfur Australian coals : a case study using micro attenuated total reflectance–fourier transform infrared (ATR–FTIR) spectrometry

The macerals in bituminous coals with varying organic sulfur content from the Early Permian Greta Coal Measures at three locations (Southland Colliery, Drayton Colliery and the Cranky Corner Basin), in and around the Sydney Basin (Australia), have been studied using light-element electron microprobe (EMP) analysis and micro-ATR–FTIR. Electron microprobe analysis of individual macerals reveals that the vitrinite in both the Cranky Corner Basin and Drayton Colliery (Puxtrees seam) samples have similar carbon contents (ca. 78% C in telocollinite), suggesting that they are of equivalent rank. However, the Cranky Corner coals have anomalously low vitrinite reflectance (down to 0.45%) vs. the Drayton materials (ca. 0.7%). They also have very high organic S content (3–6.5%) and lower O content (ca. 10%) than the equivalent macerals in the Drayton sample (0.7% S and 15.6% O). A study was carried out to investigate the impacts of the high organic S on the functional groups of the macerals in these two otherwise iso-rank, stratigraphically-equivalent seams. An iso-rank low-S coal from the overlying Wittingham Coal Measures near Muswellbrook and coals of slightly higher rank from the Greta Coal Measures at Southland Colliery near Cessnock were also evaluated using the same techniques to extend the data set. Although the telocollinite in the Drayton and Cranky Corner coals have very similar carbon content (ca.78% C), the ATR–FTIR spectra of the vitrinite and inertinite macerals in these respectively low S and high S coals show some distinct differences in IR absorbance from various aliphatic and aromatic functional groups. The differences in absorbance of the aliphatic stretching bands (2800–3000 cm−1) and the aromatic carbon (CC) peak at 1606 cm−1 are very obvious. Compared to that of the Drayton sample (0.7% S and 15% O), the telocollinite of the Cranky Corner coal (6% S and 10% O) clearly shows: (i) less absorbance from OH groups, represented by a broad region around 3553 cm−1, (ii) much stronger aliphatic C–H absorbance (stretching modes around 3000–2800 cm−1 and bending modes around 1442 cm−1) and (iii) less absorbance from aromatic carbon functional groups (peaking at 1606 cm−1). Evaluation of the iso-rank Drayton and Cranky Corner coals shows that: (i) the aliphatic C–H absorbances decrease with increasing oxygen content but increase with increasing organic S content and (ii) the aromatic H to aliphatic H ratio (Har/Hali) for the telocollinite increases with (organic) O%, but decreases progressively with increasing organic S. The high organic S content in the maceral appears to be accompanied by a greater proportion of aliphatic functional groups, possibly as a result of some of the O within maceral ring structures in the high S coal samples being replaced.

Part 1. Chemical and Physical Restraints in the Management of Mechanically Ventilated Patients in the ICU: Contributing Factors

Chemical and physical restraints are frequently used in the intensive care unit (ICU) to control agitated patients and to prevent self-harm and unplanned extubations. Published work relating to the numerous issues of the care and treatment strategies for these patients remains conflicting and unclear. Literature regarding sedation and chemical restraint reveals a trend towards management with lighter sedation, use of sedation assessment tools and sedation protocols. It remains unclear which treatment is best for agitated and delirious patients, and the evidence on the effect of sedation is conflicting. A large portion of the literature on the use of physical restraint is from general hospital wards and residential homes, and not from the ICU environment. The purpose of this paper is to provide a summary of the existing literature on the use of physical and chemical restraints in the ICU setting. In Part 1 of this two-part paper, the evidence on chemical and physical restraints is explored with specific focus on definition of terms, unplanned