Выбор оптимальных технических решений для улавливания углеводородных паров от резервуарных парков нефти

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The Elusive Third Subunit IIa of the Bacterial B-Type Oxidases: The Enzyme from the Hyperthermophile Aquifex aeolicus

The reduction of molecular oxygen to water is catalyzed by complicated membrane-bound metallo-enzymes containing variable numbers of subunits, called cytochrome c oxidases or quinol oxidases. We previously described the cytochrome c oxidase II from the hyperthermophilic bacterium Aquifex aeolicus as a ba3-type two-subunit (subunits I and II) enzyme and showed that it is included in a supercomplex involved in the sulfide-oxygen respiration pathway. It belongs to the B-family of the heme-copper oxidases, enzymes that are far less studied than the ones from family A. Here, we describe the presence in this enzyme of an additional transmembrane helix “subunit IIa”, which is composed of 41 amino acid residues with a measured molecular mass of 5105 Da. Moreover, we show that subunit II, as expected, is in fact longer than the originally annotated protein (from the genome) and contains a transmembrane domain. Using Aquifex aeolicus genomic sequence analyses, N-terminal sequencing, peptide mass fingerprinting and mass spectrometry analysis on entire subunits, we conclude that the B-type enzyme from this bacterium is a three-subunit complex. It is composed of subunit I (encoded by coxA2) of 59000 Da, subunit II (encoded by coxB2) of 16700 Da and subunit IIa which contain 12, 1 and 1 transmembrane helices respectively. A structural model indicates that the structural organization of the complex strongly resembles that of the ba3 cytochrome c oxidase from the bacterium Thermus thermophilus, the IIa helical subunit being structurally the lacking N-terminal transmembrane helix of subunit II present in the A-type oxidases. Analysis of the genomic context of genes encoding oxidases indicates that this third subunit is present in many of the bacterial oxidases from B-family, enzymes that have been described as two-subunit complexes

Converse Piezoelectricity and Ferroelectricity in Crystals of Lysozyme Protein Revealed by Piezoresponse Force Microscopy

In recent years, piezoresponse force microscopy (PFM) has been used to investigate the piezoelectric and ferroelectric behaviour of many biological materials. Piezoelectricity has been studied in fibrous proteins such as collagen [1, 2] and elastin [3], with the later also demonstrating ferroelectricity. However, a comprehensive understanding of piezoelectricity and ferroelectricity in non-fibrous proteins is lacking.Acknowledgement: Funding from the Irish Research Council Embark Postgraduate Scholarship (2012-2015) is acknowledged. CICECO and FCT are acknowledged via grant PestC/CTM/LA0011/013

Predicting glycated hemoglobin levels in the non-diabetic general population:Development and validation of the DIRECT-DETECT prediction model - a DIRECT study

AIMS/HYPOTHESIS: To develop a prediction model that can predict HbA1c levels after six years in the non-diabetic general population, including previously used readily available predictors. METHODS: Data from 5,762 initially non-diabetic subjects from three population-based cohorts (Hoorn Study, Inter99, KORA S4/F4) were combined to predict HbA1c levels at six year follow-up. Using backward selection, age, BMI, waist circumference, use of anti-hypertensive medication, current smoking and parental history of diabetes remained in sex-specific linear regression models. To minimize overfitting of coefficients, we performed internal validation using bootstrapping techniques. Explained variance, discrimination and calibration were assessed using R2, classification tables (comparing highest/lowest 50% HbA1c levels) and calibration graphs. The model was externally validated in 2,765 non-diabetic subjects of the population-based cohort METSIM. RESULTS: At baseline, mean HbA1c level was 5.6% (38 mmol/mol). After a mean follow-up of six years, mean HbA1c level was 5.7% (39 mmol/mol). Calibration graphs showed that predicted HbA1c levels were somewhat underestimated in the Inter99 cohort and overestimated in the Hoorn and KORA cohorts, indicating that the model's intercept should be adjusted for each cohort to improve predictions. Sensitivity and specificity (95% CI) were 55.7% (53.9, 57.5) and 56.9% (55.1, 58.7) respectively, for women, and 54.6% (52.7, 56.5) and 54.3% (52.4, 56.2) for men. External validation showed similar performance in the METSIM cohort. CONCLUSIONS/INTERPRETATION: In the non-diabetic population, our DIRECT-DETECT prediction model, including readily available predictors, has a relatively low explained variance and moderate discriminative performance, but can help to distinguish between future highest and lowest HbA1c levels. Absolute HbA1c values are cohort-dependent

NO binding and ultrafast dynamics in the active site of reduced heme-copper oxidases

International audienceNitric oxide (NO) is involved in regulation of respiration through interaction with the active site of cytochrome c oxidase (CcO) [1]. We study the dynamics of NO in this site in its fully reduced form by femtosecond flash photolysis. These are complicated, as more than one NO can be accommodated in or near the active site, even at very low NO concentrations [2]. By extending our measurements to the nanosecond timescale, here we show that two distinct phase of recombination of NO with heme a3 can be observed: a slow phase ( > 4 ns) which is the only phase observed at low (up to stoichiometric) NO concentrations (1 NO/enzyme), and a faster one (f250 ps) with an increasingly higher relative amplitude at higher concentrations (2 NO/enzyme). Interestingly, in CcO ba3 from Thermus thermophilus the kinetics are NO-concentration independent and consist of the slow phase only. This protein is known to have a considerable NO reductase activity [3], which prevents the steady-state simultaneous presence of 2 NO molecules in the reduced active site. Additional techniques are presently explored to test various models of NO binding and dynamics in the binuclear cente