In the present paper, the basic fundamentals of photocatalysis are explained with the influence of the five main parameters which govern the kinetics: (i) mass of catalyst, (ii) wavelength, (iii) partial pression and/or concentrations of reactants, (iv) temperature (at a second degree) and (v) the radiant flux. The main types of photocatalytic reactions presently described (all performed at room temperature) concern (i) the selective mild oxidation of hydrocarbons, (ii) the hydrogen production and (iii) the total oxidation reactions of organics in presence of water. The last point constitutes the ensemble of the last recent developments in photocatalysis. Most of organic contaminants, including dangerous pesticides, can be easily totally degraded and mineralized. Dyes are also not only decolorized, but mineralized in colored aqueous effluents. The most abundant ones (the azo-dyes) have their azo-group(s) AN@NA decomposed into N2(g), which represents an ideal decontamination case. Photocatalytic engineering is under development, now using deposited titania in a fixed bed. Some (solar) photocatalytic pilot reactors and prototypes are described. The use of solar energy as a source of activating UV-A irradiation is described as a subdiscipline called ''helio-photocatalysis''.

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followed by agglomeration of the M n 0 2 particles formed nMn02 -(Mn02)" ( 5 ) or, via 2[Mn(HzO)4(OH)21' -followed by [ Mn( H20)4(0H)OMn( H20)4( OH)] 2+ -[ M I I ( H~O )~]~+ + M n 0 2 + 3 H 2 0 (7)and reaction 5 .Equations 4 and 5 describe a process where the disproportionation occurs between two primary product molecules and is then followed by the agglomeration of MnOz formed. On the other hand, as described by eq 6 and 7, disproportionation may take place after condensation. It is even conceivable that condensation of more than two Mn(II1) species takes place before disproportionation. The induction period observed in the pulse experiments (Figure 7) may be caused by condensation to a certain size until disproportionation takes place. On the other hand, the mechanism of eq 4 and 5 also could explain the induction period, assuming that Mn02 particles of smaller size do not absorb. These reasons may also be given to explain the nonlinear behavior of the curves in Figure 2.Manganese(II1) oxide would according to these mechanisms be formed if condensation occurs much more rapidly than disproportionation. At a high degree of condensation, i.e., when colloidal manganese(II1) oxide is formed, there is no dispropor-[Mn(H20)4(OH)OMn(H20)4(OH)]2+ + H 2 0 (6) tionation. (On the contrary, in MnOl colloid containing Mn(I1) ions, even conproportionation takes place.6) According to the mechanism of eq 6 and 7, condensation would be a process of an order higher than one, while disproportionation would be a first-order-like reaction as the rate would probably not depend on particle size. High intensity of radiation should lead to a higher ratio of rates of condensation to disproportionation, Le., to a colloid of higher Mn(II1) content. This may explain why the colloid formed in neutral solution by pulse radiolysis (Figure 7, inset) contains Mn(III), while that produced by y-irradiation ( Figure 1) consists of pure Mn02. Furthermore, the presence of OH-ions (pH 8.8 in Figure 9) seems to promote efficiently the condensation process as practically pure manganese(II1) oxide is produced in pulse radiolysis. This effect may be explained by OH-addition to the [Mn(H20)4(OH)OMn(H20)4(OH)]2+ species (eq 6) or/and of higher condensation products. This also explains the decrease in conductivity during the formation of manganese(II1) oxide. An even better promotion of condensation or inhibition of disproportionation is caused by hexametaphosphate as manganese(II1) oxide is formed also in neutral solution (Figure 3). Concluding RemarksIn this work, the nature of the first product of oxidation of manganese(I1) by hydroxyl radicals was investigated in more detail than in the previous studies. The nature of the final colloidal products was also recognized. It was not possible to formulate in detail the mechanism for colloid formation, although we think that our more general outline has led to some understanding of the processes involved.The photocatalytic deposition of metallic platinum has been carried out with powder titania in aqueous susp...

The majority of organellar proteins are translated on cytosolic ribosomes and must be sorted correctly to function. Targeting routes have been identified for organelles such as peroxisomes and the endoplasmic reticulum (ER). However, little is known about the initial steps of targeting of mitochondrial proteins. In this study, we used a genome-wide screen in yeast and identified factors critical for the intracellular sorting of the mitochondrial inner membrane protein Oxa1. The screen uncovered an unexpected path, termed ER-SURF, for targeting of mitochondrial membrane proteins. This pathway retrieves mitochondrial proteins from the ER surface and reroutes them to mitochondria with the aid of the ER-localized chaperone Djp1. Hence, cells use the expanse of the ER surfaces as a fail-safe to maximize productive mitochondrial protein targeting.

The present study concerns an experimental microkinetic approach of the photocatalytic oxidation (PCO) of isopropyl alcohol (IPA) into acetone on a pure anatase TiO2 solid according to a procedure previously developed. Mainly, the kinetic parameters of each surface elementary step of a plausible kinetic model of PCO of IPA are experimentally determined: natures and amounts of the adsorbed species and rate constants (preexponential factor and activation energy). The kinetics parameters are obtained by using experiments in the transient regime with either a FTIR or a mass spectrometer as a detector. The deep oxidation (CO2 and H2O formation) of low concentrations of organic pollutants in air is one of the interests of the PCO. For IPA, literature data strongly suggest that acetone is the single route to CO2 and H2O and this explains that the present study is dedicated to the elementary steps involving gaseous and adsorbed C3H(x)O species. The microkinetic study shows that strongly adsorbed IPA species (two species denoted nd-IPA(sads) and d-IPA(sads) due to non- and dissociative chemisorption of IPA, respectively) are involved in the PCO of IPA. A strong competitive chemisorption between IPA(sads) and a strongly adsorbed acetone species controls the high selectivity in acetone of the PCO at a high coverage of the surface by IPA(sads). The kinetic parameters of the elementary steps determined in the present study are used in part 2 to provide a modeling of macroscopic kinetic data such as the turnover frequency (TOF in s(-1)) of the PCO using IPA/O2 gas mixtures.

N-terminal matrix-targeting signals (MTSs) are critical for mitochondrial protein import. Backes et al. identified additional internal MTS-like sequences scattered along the sequences of mitochondrial proteins. By binding to Tom70 on the mitochondrial surface, these sequences support the import process.

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