Infrared and Raman spectroscopic investigation of the reaction mechanism of cytochrome c oxidase

AbstractRecent progress in studies on the proton-pumping and O2 reduction mechanisms of cytochrome c oxidase (CcO) elucidated by infrared (IR) and resonance Raman (rR) spectroscopy, is reviewed. CcO is the terminal enzyme of the respiratory chain and its O2 reduction reaction is coupled with H+ pumping activity across the inner mitochondrial membrane. The former is catalyzed by heme a3 and its mechanism has been determined using a rR technique, while the latter used the protein moiety and has been investigated with an IR technique. The number of H+ relative to e− transferred in the reaction is 1:1, and their coupling is presumably performed by heme a and nearby residues. To perform this function, different parts of the protein need to cooperate with each other spontaneously and sequentially. It is the purpose of this article to describe the structural details on the coupling on the basis of the vibrational spectra of certain specified residues and chromophores involved in the reaction. Recent developments in time-resolved IR and Raman technology concomitant with protein manipulation methods have yielded profound insights into such structural changes. In particular, the new IR techniques that yielded the breakthrough are reviewed and assessed in detail. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems

EFEKTIVITAS DESORPSI CESIUM OLEH SURFAKTAN KATIONIK BERDASARKAN STRUKTUR HIDROFILIKNYA PADA MONTMORILLONIT K10

Penelitian ini membahas efisiensi desorpsi cesium (Cs) dari sampel montmorillonit K10 (MMTK10) yang telah dikontaminasi oleh Cs sebelumnya (MMTK10/Cs) menggunakan desorben surfaktan kationik benzyldodecyldimethylammonium bromida (BDAB) dan dodecyltrimethylammonium bromida (DTAB), serta HCl sebagai kontrol desorben. Hasil menunjukkan bahwa surfaktan kationik, terutama pada konsentrasi tinggi 20-50 mM, memiliki efisiensi desorpsi yang lebih tinggi dibandingkan HCl, dengan efisiensi mencapai 80-90%. Mekanisme ini dikaitkan dengan kemampuan surfaktan kationik untuk membentuk misel ketika konsentrasinya melebihi nilai konsentrasi kritis misel (KKM) atau pada konsentrasi tinggi, yang memfasilitasi pertukaran ion dengan Cs pada permukaan MMTK10/Cs. Namun, tidak ada perbedaan signifikan dalam efisiensi desorpsi Cs antara BDAB dan DTAB, meskipun struktur hidrofilik BDAB lebih besar. Hal ini berbeda dengan penelitian sebelumnya pada montmorillonit lainnya dimana semakin besar struktur hidrofilik surfaktan yang digunakan, semakin besar interlayer montmorillonit terbuka akibat masuknya surfaktan besar itu pada interlayer sehingga mendorong desorpsi Cs dengan jumlah yang lebih besar. Akan tetapi pada penelitian ini tidak adanya perbedaan efisiensi desorpsi Cs dari kedua surfaktan lebih disebabkan karena struktur clay MMTK10 itu sendiri yang tidak memiliki kemampuan pengembangan atau pembesaran interlayer, akibat perlakuan suhu saat produksinya sebelum dijual kepasaran. Selain itu, kesamaan panjang rantai ekor hidrofobik antara BDAB dan DTAB berkontribusi pada kesamaan hasil desorpsi Cs dari kedua surfaktan tersebut. Kesimpulannya, sifat dan struktur surfaktan kationik mempengaruhi proses desorpsi Cs, tetapi karakteristik spesifik dari montmorillonit atau clay yang digunakan juga berperan penting dalam mekanisme desorpsi ini.Kata kunci: Desorpsi Cs, surfaktan kationik, interlayer montmorillonit

Solute distribution in porous rhyolite as evaluated by sequential centrifugation

International audiencePore water in a porous rhyolite, having a porosity of 27% and pore radii ranging from >25 μm to 0.008 μm, was centrifugally extracted stepwise with increasing centrifugal speed to examine the potential variations of the compositions of pore water and their relationships to reaction and transport occurring in the rock. The rock was soaked for from 1 h to 7 days in an aqueous solution prior to centrifugation. To evaluate the effect of adsorption under minimum effect of dissolution, Li+ and Br− were added to the solution as tracer ions. As centrifugal speed increased, water was extracted in order of large to small pores and the thickness of residual water film became thinner. The concentrations of ions dissolving from the rock (Na+, K+, Ca2+, etc.) after 7 days of immersion were relatively constant in pores of 1−10 μm radii and exponentially increased by 3−100 fold with decreasing pore radius to 0.1 μm. These ions are dissolved from the rock and transported toward the exterior of the rock by diffusion. The calculation using a reactive-transport equation showed that the observed concentration changes reflect the change in solute distribution profile with pore size. The concentration of Si after 7 days of immersion was approximately constant or slightly decreased with increasing centrifugal speed, which appears to be controlled by the solubility. The concentration of Li+ decreased with increasing centrifugal speed after 1 h of immersion but the trend changed after 7 days of reaction. Initial behaviour of Li+ is explained by adsorption on pore walls, and the change of trend is explained by desorption of that previously adsorbed, slight amounts of dissolution, and inflow from the outside of the rock. The change in concentration of Br− with increasing centrifugal speed was small, probably because Br− was not adsorbed on the surfaces. The sequential centrifugation thus provides information on the solute distribution associated with reaction and transport occurring in rock pores

In-situ micro-FTIR Study of Thermal Changes of Organics in Tagish Lake Meteorite: Behavior of Aliphatic Oxygenated Functions and Effects of Minerals

Systematic in-situ FTIR heating experiments of Tagish Lake meteorite grains have been performed in order to study thermal stability of chondritic organics. Some aliphatic model organic substances have also been used to elucidate effects of hydrous phyllosilicate minerals on the thermal stability of organics. The experimental results indicated that organic matter in the Tagish Lake meteorite might contain oxygenated aliphatic hydrocarbons which are thermally stable carbonyls such as ester and/or C=O in ring compounds. The presence of hydrous phyllosilicate minerals has a pronounced effect on the increase of the thermal stability of aliphatic and oxygenated functions. These oxygenated aliphatic organics in Tagish Lake can be formed during the aqueous alteration in the parent body and the formation temperature condition might be less than 200 C, based especially on the thermal stability of C-O components. The hydrous phyllosilicates might provide sites for organic globule formation and protected some organic decompositio

2-Mercaptoethylamine, a competitive inhibitor of spermidine synthase in mammalian cells

AbstractSpermidine synthase from rat ventral prostate was inhibited by 2-mercaptoethylamine (MEA). Inhibition of spermidine synthase by MEA was competitive with respect to one of the substrates putrescine, but not competitive with respect to the other substrate decarboxylated S-adenosylmethionine. MEA markedly depressed spermidine and spermine contents in human erythroid leukemia K562 cells, suggesting that these changes resulted from the inhibitory effect of MEA on spermidine synthase in situ

Experimental alteration of a meteoritic model-glass in different media

A meteoritic model-glass has been altered under oxidizing conditions in different media (water and sulfuric acid) at 80℃ and 0℃. The reactions were followed by analysis of solutions and solids (XRD, FTIR, SEM, TEM). After reaction, all the elements were detected in solution, at different levels of concentration related to the medium. The most aggressive media were sulfuric acid at pH 1 for 80℃ and 0℃ runs. In such alteration conditions, the surface of the solid evolved rapidly according to the temperature. At 80℃, one noticed the development of a Si-rich layer containing calcium and sulfate ions which combined to form gypsum. At 0℃, only smooth surface with etch pits and scarce gypsum crystals were observed. In contact with glass, ultramicrotomed thin-sections studied by TEM revealed the presence of two kinds of products : Fe-Al silicate phases (in deionized water and H_2SO_4 solution with pH_4) and a high-silica content layer (H_2SO_4 solution with pH1,at 80℃)

Rapid Contamination During Storage of Carbonaceous Chondrites Prepared for Micro FTIR Measurements

The carbonaceous chondrites Tagish Lake and Murchison, which contain abundant hydrous minerals, when pressed on aluminum plates and analyzed by micro FTIR, were found to have been contaminated during brief (24 hours) storage. This contamination occurred when the samples were stored within containers which included silicone rubber, silicone grease or adhesive tape. Long-path gas cell FTIR measurements for silicone rubber revealed the presence of contaminant volatile molecules having 2970 cm(sup -1) (CH3) and 1265 cm(sup -1) (Si-CH3) peaks. These organic contaminants are found to be desorbed by in-situ heating infrared measurements from room temperature to 200-300 C. Careful preparation and storage are therefore needed for precious astronomical samples such as meteorites, IDPs and mission returned samples from comets, asteroids and Mars, if useful for FTIR measurements are to be made

Krafft temperature and enthalpy of solution of N-acyl amino acid surfactants and their racemic modifications: Effect of the amino acid residue

金沢大学工学部The Krafft temperatures and the enthalpies of solution of six kinds of N-hexadecanoyl amino acid surfactant (Gly, Ala, Val, Leu, Ile, and Phe) were obtained from both solubility measurements and differential scanning calorimetry. It was shown that the Krafft temperature of N-hexadecanoyl amino acid surfactant increased with decreasing size of the amino acid residue except for the case of phenylalanine. On the other hand, the enthalpy of solution was endothermic and increased with decreasing size of the amino acid residue except for the cases of glycine and phenylalanine. It was found from these results that the D-L interaction was superior to the L-L interaction in solid state of N-hexadecanoyl amino acid surfactant salt for both the alanine and phenylalanine systems. It was suggested by ab initio calculations that the difference of the magnitude of the peptide-peptide hydrogen bonding was the dominant factor for the chiral effect

Krafft temperature and enthalpy of solution of N-acyl amino acid surfactants and their racemic modifications: Effect of the counter ion

金沢大学工学部The Krafft temperatures and enthalpies of solution of N-hexadecanoyl alaninate and valinate, and N-tetradecanoyl phenylalaninate were obtained from differential scanning calorimetry. The Krafft temperature of N-acyl amino acid surfactant increased with decreasing size of the counter ion, with some exceptions. The enthalpy of solution was endothermic and increased with decreasing size of the counter ion except for the cases of lithium salt. The results showed that the L-L interaction in the solid state of N-hexadecanoyl amino acid surfactant salt was superior to the D-L interaction for both the alanine and valine systems when the counter ion size increased. However, the D-L interaction was still advantageous for the phenylalanine system with Cs+ as a counter ion. Both Fourier transform infrared spectroscopy studies and theoretical calculations suggested that the difference in magnitudes of the interactions between peptide and counter ion was a dominant factor for the chiral effect