Simulating the low-temperature, metastable electrochromism of Photosystem I: Applications to Thermosynechococcus vulcanus and Chroococcidiopsis thermalis.

Low-temperature, metastable electrochromism has been used as a tool to assign pigments in Photosystem I (PS I) from Thermosynechococcus vulcanus and both the white light and far-red light (FRL) forms of Chroococcidiopsis thermalis. We find that a minimum of seven pigments is required to satisfactorily model the electrochromism of PS I. Using our model, we provide a short list of candidates for the chlorophyll f pigment in FRL C. thermalis that absorbs at 756 nm, whose identity, to date, has proven to be controversial. Specifically, we propose the linker pigments A40 and B39 and two antenna pigments A26 and B24 as defined by crystal structure 1JB0. The pros and cons of these assignments are discussed, and we propose further experiments to better understand the functioning of FRL C. thermalis.

Accuracy of eight-polar bioelectrical impedance analysis for the assessment of total and appendicular body composition in peritoneal dialysis patients.

OBJECTIVE: To establish the accuracy of bioelectrical impedance analysis (BIA) for the assessment of total and appendicular body composition in peritoneal dialysis (PD) patients. DESIGN: Cross-sectional study. SETTING: University Nephrology Clinic. SUBJECTS: In all, 20 PD patients and 77 healthy controls matched for gender, age and body mass index. METHODS: Whole-body fat-free mass (FFM) and appendicular lean tissue mass (LTM) were measured by dual-energy X-ray absorptiometry. Resistance (R) of arms, trunk and legs was measured by eight-polar BIA at frequencies of 5, 50, 250 and 500 kHz. Whole-body resistance was calculated as the sum of R of arms, trunk and legs. The resistance index (RI) was calculated as the ratio between squared height and whole-body or segmental R. RESULTS: RI at 500 kHz was the best predictor of FFM, LTM(arm) and LTM(leg) in both PD patients and controls. Equations developed on controls overestimated FFM and LTM(arm) and underestimated LTM(leg) when applied to PD patients. Specific equations were thus developed for PD patients. Using these equations, the percent root mean-squared errors of the estimate for PD patients vs controls were 5 vs 6% for FFM, 8 vs 8% for LTM(arm) and 7 vs 8% for LTM(leg). CONCLUSION: Eight-polar BIA offers accurate estimates of total and appendicular body composition in PD patients, provided that population-specific equations are used.

Cross-calibration of eight-polar bioelectrical impedance analysis versus dual-energy X-ray absorptiometry for the assessment of total and appendicular body composition in healthy subjects aged 21-82 years.

AIM: To calibrate eight-polar bioelectrical impedance analysis (BIA) against dual-energy X-ray absorptiometry (DXA) for the assessment of total and appendicular body composition in healthy adults. RESEARCH DESIGN: A cross-sectional study was carried out. SUBJECTS: Sixty-eight females and 42 males aged 21-82 years participated in the study. METHODS: Whole-body fat-free mass (FFM) and appendicular lean tissue mass (LTM) were measured by DXA; resistance (R) of arms, trunk and legs was measured by eight-polar BIA at frequencies of 5, 50, 250 and 500 kHz; whole-body resistance was calculated as the sum R of arms, trunk and legs. RESULTS: The resistance index (RI), i.e. the height(2)/resistance ratio, was the best predictor of FFM and appendicular LTM. As compared with weight (Wt), RI at 500 kHz explained 35% more variance of FFM (vs 0.57), 45% more variance of LTM(arm) (vs 0.48) and 36% more variance of LTM(leg) (vs 0.50) (p < 0.0001 for all). The contribution of age to the unexplained variance of FFM and appendicular LTM was nil or negligible and the RI x sex interactions were either not significant or not important on practical grounds. The percent root mean square error of the estimate was 6% for FFM and 8% for LTM(arm) and LTM(leg). CONCLUSION: Eight-polar BIA offers accurate estimates of total and appendicular body composition. The attractive hypothesis that eight-polar BIA is influenced minimally by age and sex should be tested on larger samples including younger individuals.

Acerca de la muerte del rey Herodes el Grande / About the death of Herod the Great

Herod the Great was the founder of a dynasty that reigned on Judea for several generations. His birth date is estimated on year 73 AC and died at 70 years old. Descriptions of the final disease of Herod were obtained from the classical chronicles of Flavius Josephus, The Jewish war and Jewish Antiquities. A medical explanation for his death is attempted. A parasitism caused by Schistosoma haematobium is suggested as the etiology for chronic renal failure (edema, halitosis and orthopnea) and a "gangrene of genitalia that engendered worms" in the words of Josephus. This would be explained by the formation of genital and urinary fistulae, observed in such disease. The asseveration that Herod was attacked by black bilis is also discussed, based on the concepts of the Hippocratic medicine of that time.

Accuracy of an eight-point tactile-electrode impedance method in the assessment of total body water.

OBJECTIVE: To establish the accuracy of an eight-polar tactile-electrode impedance method in the assessment of total body water (TBW). DESIGN: Transversal study. SETTING: University department. SUBJECTS: Fifty healthy subjects (25 men and 25 women) with a mean (s.d.) age of 40 (12) y. METHODS: TBW measured by deuterium oxide dilution; resistance (R) of arms, trunk and legs measured at frequencies of 5, 50, 250 and 500 kHz with an eight-polar tactile-electrode impedance-meter (InBody 3.0, Biospace, Seoul, Korea). RESULTS: An algorithm for the prediction of TBW from the whole-body resistance index at 500 kHz (height (2)/R(500) where R is the sum of the segmental resistances of arms, trunk and legs) was developed in a randomly chosen subsample of 35 subjects. This algorithm had an adjusted coefficient of determination (r2(adj)) of 0.81 (P<0.0001) and a root mean square error (RMSE) of 3.6 l (9%). Cross-validation of the predictive algorithm in the remaining 15 subjects gave an r2(adj) of 0.87 (P<0.0001) and an RMSE of 3.0 l (8%). The precision of eight-polar BIA, determined by measuring R three times a day for five consecutive days in a fasting subject, was < or =2.8% for all segments and frequencies. CONCLUSION: Eight-polar BIA is a precise method that offers accurate estimates of TBW in healthy subjects. This promising method should undergo further studies of precision and its accuracy in assessing extracellular water and appendicular body composition should be determined. SPONSORSHIP: Modena and Reggio Emilia University.

Manipulating redox systems: application to nanotechnology.

Redox proteins and enzymes are attractive targets for nanobiotechnology. The theoretical framework of biological electron transfer is increasingly well-understood, and several properties make redox centres good systems for exploitation: many can be detected both electrochemically and optically; they can perform specific reactions; they are capable of self-assembly; and their dimensions are in the nanoscale. Great progress has been made with the two main approaches of protein engineering: rational design and combinatorial synthesis. Rational design has put our understanding of the structure-function relationship to the test, whereas combinatorial synthesis has generated new molecules of interest. This article provides selected examples of novel approaches where redox proteins are "wired up" in efficient electron-transfer chains, are "assembled" in artificial multidomain structures (molecular Lego), are "linked" to surfaces in nanodevices for biosensing and nanobiotechnological applications.

Engineering and design in the bioelectrochemistry of metalloproteins.

Engineered metalloproteins offer interesting systems for electrochemical studies of protein structure/function and their applications in nanobiotechnology. Scanning probe microscopy and cyclic voltammetry of engineered metalloproteins and electrodes have proved to be a powerful combination of tools contributing to the field of bioelectrochemistry. The ability to engineer tags, such as histidine tags and biotin-acceptor peptides, and to site-specifically introduce cysteine residues enabled the creation of ordered immobilised protein structures that can be characterised both electrochemically and topographically. Gene fusion and de novo combinatorial synthesis of metalloproteins are emerging to provide structures with the desired electrochemical properties.

Engineering artificial redox chains by molecular 'Lego'.

This work reports on a novel approach for building artificial redox chains: the molecular 'Lego' approach. This exploits the scaffold of natural redox proteins by fusing together functional protein modules with the desired properties. The molecular 'Lego' mimics the natural molecular evolution that proceeded by modular assembly of genes/DNA segments. Non-physiological electron transfer partners, flavodoxin (fld) and cytochrome c553 (c553) from Desulfovibrio vulgaris and the haem domain of P450 BM3 (BMP) from Bacillus megaterium have been used as building blocks in different combinations to build artificial redox chains. The kinetic characterization of the electron transfer (ET) between the separate building blocks has been carried out. Under pseudo-first order conditions, a limiting ET rate, klim, of 0.48 +/- 0.05 s-1 and 43.77 +/- 2.18 s-1 and an apparent binding constant, Kapp, of 21 +/- 6 microM and 1.23 +/- 0.32 microM have been found for the fld/c553 and fld/BMP redox pairs, respectively. These results show that fld can be used as a module for transferring electrons to c553 and BMP. A 3D model of the fld/c553 and fld/BMP complexes was used to guide the construction of covalently linked assemblies via engineered disulfide bridges or by fusion of the relevant genes via an engineered loop. The first approach led to the construction, expression and characterization of the S35C and S64C mutants of fld and M23C and G51C mutants of c553. Although the redox potentials of the separate mutants were found to be the same as those of recombinant wild type proteins (-408 mV for the semiquinone/hydroquinone couple of fld and +32 mV for the c553), the c553 homo-dimers M23C-M23C and G51C-G51C were found to have redox potentials of +88 and +105 mV, respectively. These differences have been analysed in terms of exposure of the haem cofactors to the solvent, and these lead to some interesting questions on the redox potentials of the transient redox complexes in physiological systems. The fld-c553 S64C-M23C and S35C-M23C chimeras were constructed, expressed and purified but the FMN was found to be destabilised resulting in the apo-form of these proteins. The gene fusion strategy was used to produce covalently linked assemblies of both fld-c553 and fld-BMP. The former was expressed using a seven amino acid (GPGPGPG) loop linking the C-terminus of fld to the N-terminus of c553. The fld-BMP fusion protein was successfully expressed by using the naturally occurring loop of the P450 BM3 (residues 471-479) to link the BMP domain at the N-terminus with fld domain at the C-terminus. This fusion was found to be correctly folded and functional. Efficient ET from the FMN to the haem domain (370 s-1) was also found to be in the same region of the physiological redox partners (250 s-1). This work demonstrates the feasibility of the molecular 'Lego' approach in generating functional multi-domain proteins with designed properties, beyond the restrictions imposed by the naturally occurring protein domains.

Release of retinol and denaturation of its plasma carrier, retinol-binding protein.

BACKGROUND: Retinol is tightly packed inside the structure of its plasma carrier (retinol-binding protein, RBP). It was found that retinol release from RBP to aqueous solutions is facilitated by either very low pH or very high temperatures (i.e. by non-physiological conditions that cause protein denaturation). It was also found that alcohols induce protein conformational transitions to denatured states. On this basis, it may be suggested that retinol release in vivo is facilitated by the partial unfolding of the carrier resulting from the concerted action of the moderate local decrease of pH and the moderate local decrease of dielectric constant in proximity to the target membranes. RESULTS: In vitro, at 37 degrees C, retinol is removed from its plasma carrier by the concerted action of the moderately low pH and the moderately low dielectric constant of solutions containing a low ionic strength buffer and methanol in variable proportions. Release of retinol is accompanied by a conformational transition of RBP from the native to the molten-globule state. CONCLUSIONS: The physiological function of RBP-targeted delivery of retinol-is mimicked in vitro by the facilitated release of retinol (associated with a partial unfolding of the protein carrier) in solutions exhibiting pH and dielectric constant values that are within the range of values expected in the in vivo microenvironment.

Natural history of nutrition in chronic renal failure.

Dietetic manipulation significantly influences the progression of renal failure in laboratory animals. Clinical results in humans are contradictory. The aim of the study was epidemiological research on a large sample of kidney disease patients to verify whether renal failure influences nutrient intake before dietetic manipulation. Four hundred and forty-one consecutive, non-selected adult patients with renal insufficiency (creatinine 133-963 mumol, mean 301 +/- 178 mumol in male, 288 +/- 156 mumol/l in female) and 43 kidney disease patients without renal failure were enrolled in the prospective study in the period 1988-1995. Interview at the time of the first nephrological check was performed by only one dietician; the record by recall of intake over 7 days with quantitative assessment was collected with the assistance of nutritional dossier and photographic measures. The patients with renal failure consume energy, proteins, lipids and carbohydrates in lesser quantities than the national population of the same geographical area, but the total lipid and monounsaturated fatty acid intake is higher compared with Italian dietary reference values. In patients with renal failure mean protein intake was 1.02 +/- 0.2 g/kg/day in males and 0.96 +/- 0.2 g/kg/day in females; mean lipid intake was 1.10 +/- 0.2 g/kg/day in males and 1.17 +/- 0.3 g/kg/day in females; mean carbohydrate intake was 3.7 +/- 1.1 g/kg/day in males and 3.49 +/- 1 g/kg/day in females. The nutrition alterations observed in chronic renal failure may be a biological adaptation due to neurological changes affecting the sense of taste.

Identification of polycyclic aromatic hydrocarbons in carbon black with reference to cancerogenic risk in tire production.

Carbon blacks used in tire production have been examined for their polycyclic aromatic hydrocarbons (P.A.H.) content. The analytical procedures commonly adopted are discussed. The results obtained show that, A benzene extraction time of 250 hours is necessary to obtain complete extraction, but for practical purposes, an extraction time of 150 hours is sufficient to extract more than 95% of the PAH. It is possible to identify two classes of blacks in regard to extractables. The one class provides extractables in the range of 200--400 micrograms/g; the second class, in the range of 1000--2000 micrograms/g. No P.A.H. were detected by direct injection of carbon black into the mass spectrograph at 200 degrees C, 10(-6) torr. This was probably due to the very strong bonding to the black particles. The P.A.H. contribute a relative constant percentage of the benzene extracts. It is reasonably possible to exclude any carcinogenic risk to personnel, in a working environment, with an airborne carbon black concentration equal to or less than 3.5 mg/m3, due to the very low P.A.H. content of carbon black and to the very strong P.A.H. bonding to the black particles.