Understanding differential aspects of microdiffusion (channeling) in the Coenzyme Q and Cytochrome c regions of the mitochondrial respiratory system

Over the past decades, models of the organization of mitochondrial respiratory system have been controversial. The goal of this perspective is to assess this “conflict of models” by focusing on specific kinetic evidence in the two distinct segments of Coenzyme Q- and Cytochrome c-mediated electron transfer. Respiratory supercomplexes provide kinetic advantage by allowing a restricted diffusion of Coenzyme Q and Cytochrome c, and short-range interaction with their partner enzymes. In particular, electron transfer from NADH is compartmentalized by channeling of Coenzyme Q within supercomplexes, whereas succinate oxidation proceeds separately using the free Coenzyme Q pool. Previous evidence favoring Coenzyme Q random diffusion in the NADH-dependent electron transfer is due to downstream flux interference and misinterpretation of results. Indeed, electron transfer by complexes III and IV via Cytochrome c is less strictly dependent on substrate channeling in mammalian mitochondria. We briefly describe these differences and their physiological implications

The Stillwater Complex chromitites : the response of chromite crystal chemistry to magma injection

Nineteen chromite crystals from the A, B, E, G, H, J and K chromitite layers of the Peridotite Zone of the Stillwater Complex (Montana, USA) have been studied by means of X-ray single crystal diffraction and microprobe analyses. The results show that samples from the basal A layer are quite different from the others showing very high oxygen positional parameter u (0.2633-0.2635) and Ti- contents (0.059-0.067apfu). Mg# values are within the range 0.21-0.23 while for the other chromites it is in the range 0.45-0.47. Moreover, for the other samples, according to the structural parameters, two groups have been identified. The first one comprises samples of layers B, E and G, the second includes H, J and K layer samples. It is supposed that high Fe2+ and Ti contents of A layer samples are due to the post-crystallization reaction with interstitial liquid. This fact allowed a very slow cooling rate as evidenced by the high u values. The fractionation of evolved magma from within the intrusion and pulse of a new magma bringing more chromium into the chamber lead to Cr- and Fe3+ -rich compositions and consequently to the increase of the cell edges. The decrease of u values seems to be related to the Cr+Fe3+ and/or Al contents

Is supercomplex organization of the respiratory chain required for optimal electron transfer activity?

AbstractThe supra-molecular assembly of the main respiratory chain enzymatic complexes in the form of “supercomplexes” has been proved by structural and functional experimental evidence. This evidence strongly contrasts the previously accepted Random Diffusion Model stating that the complexes are functionally connected by lateral diffusion of small redox molecules (i.e. Coenzyme Q and cytochrome c).This review critically examines the available evidence and provides an analysis of the functional consequences of the intermolecular association of the respiratory complexes pointing out the role of Coenzyme Q and of cytochrome c as channeled or as freely diffusing intermediates in the electron transfer activity of their partner enzymes

Ship-board report on atmospheric CO2 concentrations recorded on continuous from Mediterranean sea to Antarctica

We present the results obtained from continuous measurements performed during two cruises with hemispherical courses. In this way, we obtained the latitudinal trend of CO2 in continuity of space and time along two hemispheric courses in 1994-95 and 1996-97 from Europe to Antarctica. The results are compared with measurements from the National Oceanic and Atmospheric Administration (NOAA) Climate Monitoring and Diagnostic Laboratory (CMDL) cooperative air sampling network. The fitting of data recorded on board with the historical data sets recorded at Palmer Station is also presented, highlighting the current annual increase in atmospheric CO2 concentrations

A multi-analytical study of Bronze Age pottery from the UNESCO site of Al-Khutm (Bat, Oman)

The extensive investigation carried out in recent years at the UNESCO site of Al-Khutm (Ibri, Oman) has allowed to uncover the monumental remains of a tower dated back to the third millennium BC and to collect an abundant ceramic assemblage from the associated soil deposits. Eighteen selected pottery samples have been investigated using a multi-analytical approach including microfocus X-ray computed tomography, X-ray diffraction, optical microscopy and prompt gamma activation analysis to analyse the vessel-forming technique and to characterise their micro-structure, mineralogical and chemical composition to recognise possible local vs. non-local raw materials. The results provided new insights on ancient manufacturing processes and revealed that most of the vessels were locally produced exploiting raw materials from the surroundings of the site with the exception of a fragment of a black slipped jar. The chemical results suggest that the latter was imported from the Indus area in nowadays Pakistan. This evidence integrates our knowledge about the presence of this type of vessels in Oman and confirms the involvement of inland centres like Bat and Al-Khutm into a large-scale exchange system

Inhibitor sensitivity of respiratory complex I in human platelets: A possible biomarker of ageing

AbstractNADH-Coenzyme Q reductase was assayed in platelet mitochondrial membranes obtained from 19 pools of two venous blood samples from female young (19–30 years) individuals and 18 pools from aged ones (66–107 years). The enzyme activities were not significantly changed in the two groups, but a decrease of sensitivity to the specific inhibitor, rotenone, occurred in a substantial number of aged individuals. The results are in agreement with the predictions of the mitochondrial theory of ageing and may be used to develop a sensitive biomarker of the ageing process

Distribution of Capillary Transit Times in Isolated Lungs of Oxygen-Tolerant Rats

Rats pre-exposed to 85% O2 for 5–7 days tolerate the otherwise lethal effects of 100% O2. The objective was to evaluate the effect of rat exposure to 85% O2 for 7 days on lung capillary mean transit time (t¯c) and distribution of capillary transit times (h c(t)). This information is important for subsequent evaluation of the effect of this hyperoxia model on the redox metabolic functions of the pulmonary capillary endothelium. The venous concentration vs. time outflow curves of fluorescein isothiocyanate labeled dextran (FITC-dex), an intravascular indicator, and coenzyme Q1 hydroquinone (CoQ1H2), a compound which rapidly equilibrates between blood and tissue on passage through the pulmonary circulation, were measured following their bolus injection into the pulmonary artery of isolated perfused lungs from rats exposed to room air (normoxic) or 85% O2 for 7 days (hyperoxic). The moments (mean transit time and variance) of the measured FITC-dex and CoQ1H2 outflow curves were determined for each lung, and were then used in a mathematical model [Audi et al. J. Appl. Physiol. 77: 332–351, 1994] to estimate t¯c and the relative dispersion (RDc) of h c(t). Data analysis reveals that exposure to hyperoxia decreases lung t¯c by 42% and increases RDc, a measure h c(t) heterogeneity, by 40%