Photoreaction of tyrosin-iodinated bacteriorhodopsin at low temperature

1982 ◽  
Vol 2 (11) ◽  
pp. 949-958 ◽  
Author(s):  
Tatsuo Iwasa ◽  
Kazuo Takeda ◽  
Fumio Tokunaga ◽  
Peter S. Scherrer ◽  
Lester Packer
Keyword(s):  
Low Temperature ◽  
Proton Pump ◽  
Photochemical Reaction ◽  
Room Temperature ◽  
Green Light ◽  
Glycerol Solution ◽  
Difference Spectra ◽  
Tyrosine Residues ◽  
The Difference

To elucidate the role of tyrosine residues in the shift of λmax and the light-driven proton pump of bacteriorhodopsin, the photochemical reaction of tyrosine-iodinated bacteriorhodopsin (tyr-mod-bR) was investigated by low-temperature spectrophotometry. After 4–5 of 11 tyrosine residues of bacteriorhodopsin were iodinated, the meta-intermediate of tyr-mod-bR in 75% glycerol solution became so stable that its decay could be observed even at room temperature and it was stable in the dark for several hours at −65°C. Four batho-intermediates were formed by irradiation with green light (500 nm) at −170°C. Like native bacteriorhodopsin, these batho-intermediates were photoreversible at −170°C. Four corresponding meta-intermediates were also formed by irradiation at −60°C. Using the difference spectra between meta-intermediates and tyr-mod-bR, the absorption spectra of four kinds of tyr-mod-bRs, batho-intermediates, and meta-intermediates were estimated. Each was at shorter wavelengths than that of its corresponding type in native bacteriorhodopsin. The results indicate that two or more tyrosine residues have some role in determining color in native bacteriorhodopsin.

scholarly journals Multiple light-induced reactions of cytochromes b and c in Rhodopseudomonas spheroides

1969 ◽  
Vol 114 (4) ◽  
pp. 793-799 ◽  
Author(s):  
O. T. G. Jones
Keyword(s):  
Cytochrome C ◽  
Cytochrome B ◽  
Photochemical Reaction ◽  
Room Temperature ◽  
Close Association ◽  
Antimycin A ◽  
Reaction Centre ◽  
Difference Spectra ◽  
Cytochromes C ◽  
Rhodopseudomonas Spheroides

Illumination of chromatophore preparations from Rhodopseudomonas spheroides causes the oxidation of a cytochrome c and a slight oxidation of a cytochrome b with a maximum at 560nm. When illuminated in the presence of antimycin A the oxidation of cytochrome c was more pronounced and cytochrome b560 was reduced; the dark oxidation of cytochrome b560 was biphasic in the presence of succinate, but not in the presence of NADH, a less effective reductant. Split-beam spectroscopy showed that, in addition to the reduction of cytochrome b560, another pigment with maxima at 565 and 537nm. was reduced and was more rapidly oxidized in the dark than cytochrome b560. This pigment, tentatively identified as cytochrome b565, was also detected in spectra at 77°k, after brief illumination at room temperature; the maxima at 77°k were at 562 and 536nm. In the absence of antimycin A, light caused a transient reduction of cytochrome b565 and an oxidation of cytochrome b560. Dark oxidation of b565 was rapid, even in the presence of antimycin A and succinate. Difference spectra, at 77°k, of ascorbate-reduced minus succinate-reduced chromatophores or of anaerobic succinate-reduced minus aerobic succinate-reduced chromatophores suggested that two cytochromes c were present, with maxima at 547 and 549nm. When chromatophores frozen at 77°k were illuminated both these cytochromes c were oxidized, indicating a close association with the photochemical reaction centre. A scheme involving two reaction centres is proposed to explain these results.

The role of hydrogen bonds in order-disorder transition of a new incommensurate low temperature phase β-[Zn-(C7H4NO4)2]·3H2O

2018 ◽  
Vol 233 (1) ◽  
pp. 17-25 ◽  
Author(s):  
Masoumeh Tabatabaee ◽  
Morgane Poupon ◽  
Václav Eigner ◽  
Přemysl Vaněk ◽  
Michal Dušek
Keyword(s):  
Low Temperature ◽  
Hydrogen Bonds ◽  
Dicarboxylic Acid ◽  
Room Temperature ◽  
Temperature Phase ◽  
Temperature Structure ◽  
Modulated Structure ◽  
Q Vector ◽  
Low Temperature Phase

AbstractThe room temperature structure withP21/csymmetry of the zinc(II) complex of pyridine-2,6-dicarboxylic acid was published by Okabe and Oya (N. Okabe, N. Oya, Copper(II) and zinc(II) complexes of pyridine-2,6-dicarboxylic acid.Acta Crystallogr. C.2000,56, 305). Here we report crystal structure of the low temperature phaseβ-[Zn(pydcH)2]·3H2O, pydc=C7H3NO4, resulting from the phase transition around 200K. The diffraction pattern of the low temperature phase revealed satellite reflections, which could be indexed with q-vector 0.4051(10)b* corresponding to (3+1)Dincommensurately modulated structure. The modulated structure was solved in the superspace groupX21/c(0b0)s0, whereXstands for a non-standard centring vector (½, 0, 0, ½), and compared with the room temperature phase. It is shown that hydrogen bonds are the main driving force of modulation.

scholarly journals Carbon monoxide-reacting haemoproteins in the mitochondrial fraction of Acanthamoeba castellanii

1980 ◽  
Vol 186 (3) ◽  
pp. 669-678 ◽  
Author(s):  
S W Edwards ◽  
D Lloyd
Keyword(s):  
Carbon Monoxide ◽  
Low Temperature ◽  
Room Temperature ◽  
Acanthamoeba Castellanii ◽  
Mitochondrial Fraction ◽  
Submitochondrial Particles ◽  
Difference Spectra ◽  
Intact Cells ◽  
Mitochondrial Fractions ◽  
Eukaryotic Organisms

1. Room-temperature (18 degrees C) CO difference spectra of mitochondrial fractions from the amoeba Acanthamoeba castellanii reveal the presence of at least four CO-reacting haemoproteins. As well as cytochrome a3, other components reacting with CO are: (i) a c-type cytochrome; (ii) a b-type cytochrome; and (iii) another a-type cytochrome. 2. The same components can be identified in low-temperature photodissociation experiments with intact cells or mitochondria. 3. The time of exposure to CO and the nature of the reductant are both important in identifying all the components present, in that the b-type cytochrome is more readily distinguished after longer exposure to CO and more of the c-type cytochrome is detectable when NADH is the reductant 4. Treatment of mitochondria with ultrasound releases two components, identifiable in low-temperature difference spectra as a c-type and a b-type cytochrome; only the latter appears to have any reaction with CO, and the CO-reacting c-type cytochrome is retained in submitochondrial particles. 5. The complexity of the CO-reacting haemoproteins in this organism is compared with the simpler systems found in other eukaryotic organisms.

Electron Density in YTiO3

1997 ◽  
Vol 53 (5) ◽  
pp. 739-744 ◽  
Author(s):  
J. R. Hester ◽  
K. Tomimoto ◽  
H. Noma ◽  
F. P. Okamura ◽  
J. Akimitsu
Keyword(s):  
Low Temperature ◽  
Electron Density ◽  
Title Compound ◽  
Room Temperature ◽  
Local Environment ◽  
Consistent Difference ◽  
Crystal Data ◽  
Alpha Radiation ◽  
Coordination Polyhedra

Accurate electron density analyses have been performed on the title compound, yttrium titanate, at room and low temperature using W K\alpha radiation. Room- and low temperature \delta\rho maps are generally consistent. Difference electron densities near the two symmetrically independent O atoms differ markedly. These observations may have significance for understanding the role of the O atom in mediating d-electron interactions between neighbouring Ti coordination polyhedra. Features having lower symmetry than that of the approximately octahedral local environment are observed within the Ti coordination octahedron. Crystal data at room temperature: YTiO3, M r = 184.79, T = 293 K, Pnma, a = 5.6901 (4), b = 7.6130 (7), c = 5.3381 (6) Å, V = 231.24 (4) Å3, Z = 4, D x = 5.308 Mg m-3, \mu(W K\alpha) = 1.02 mm−1, R = 0.024, wR = 0.017, S = 1.64 (2) for 2996 independent reflections. Low temperature: T = 127 K, Pnma, a = 5.690 (4), b = 7.583 (6), c = 5.318 (5) Å, V = 229.5 (3) Å3, D x = 5.35 Mg m−3, \mu(W K\alpha) = 1.02 mm−1, R = 0.021, wR = 0.015, S = 1.80 (2) for 2968 independent reflections.

scholarly journals Evidence for an essential histidine residue in d-xylose isomerases

1988 ◽  
Vol 250 (1) ◽  
pp. 153-160 ◽  
Author(s):  
W Vangrysperre ◽  
M Callens ◽  
H Kersters-Hilderson ◽  
C K De Bruyne
Keyword(s):  
Xylose Isomerase ◽  
Lactobacillus Brevis ◽  
Histidine Residue ◽  
Difference Spectra ◽  
Streptomyces Sp ◽  
Histidine Residues ◽  
Tyrosine Residues ◽  
Diethyl Pyrocarbonate ◽  
The Difference ◽  
Streptomyces Violaceoruber

Diethyl pyrocarbonate inactivated D-xylose isomerases from Streptomyces violaceoruber, Streptomyces sp., Lactobacillus xylosus and Lactobacillus brevis with second-order rate constants of 422, 417, 99 and 92 M-1.min-1 respectively (at pH 6.0 and 25 degrees C). Activity was completely restored by the addition of neutral hydroxylamine, and total protection was afforded by the substrate analogue xylitol in the presence of either Mg2+ or Mn2+ according to the genus studied. The difference spectra of the modified enzymes revealed an absorption maximum at 237-242 nm, characteristic for N-ethoxycarbonylhistidine. In addition, the spectrum of ethoxycarbonylated D-xylose isomerase from L. xylosus showed absorption minima at both 280 and 230 nm, indicative for modification of tyrosine residues. Nitration with tetranitromethane followed by diethyl pyrocarbonate treatment eliminated the possibility that modification of tyrosine residues was responsible for inactivation, and resulted in modification of one non-essential tyrosine residue and six histidine residues. Inactivation of the other D-xylose isomerases with diethyl pyrocarbonate required the modification of one (L. brevis), two (Streptomyces sp.) and four (S. violaceoruber) histidine residues per monomer. Spectral analysis and maintenance of total enzyme activities further indicated that either xylitol Mg2+ (streptomycetes) or xylitol Mn2+ (lactobacilli) prevented the modification of one crucial histidine residue. The overall results thus provide evidence that a single active-site histidine residue is involved in the catalytic reaction mechanism of D-xylose isomerases.

Photochemical reactions of bacteriorhodopsin in Triton X-100 solution studied by low temperature spectrophotometry

1985 ◽  
Vol 63 (7) ◽  
pp. 1891-1898 ◽  
Author(s):  
Tatsuo Iwasa ◽  
Fumio Tokunaga ◽  
Tỏru Yoshizawa
Keyword(s):  
Low Temperature ◽  
Thermal Equilibrium ◽  
Photochemical Reaction ◽  
Membrane Structure ◽  
Purple Membrane ◽  
Photochemical Reactions ◽  
The Other ◽  
Other Hand ◽  
Triton X

The photochemical reaction of purple membrane solubilized with Triton X-100 (T-BR) was investigated by low temperature spectrophotometry. The batho- and meta-intermediates of T-BR were observed to resemble bacteriorhodopsin in native purple membrane. Two photoproducts characteristic of the T-BR system were found, which were named the "490-nm complex" and the "380-nm complex". The 490-nm complex was in thermal equilibrium with T-BR in the dark. Cooling T-BR to low temperature favoured the 490-nm complex, which was photoinsensitive. On the other hand, the 380-nm complex was produced by warming the batho-intermediate and reverted to the original T-BR. The meta-intermediate of T-BR may possibly be in thermal equilibrium with the 380-nm complex. On the basis of the above results, the possible role of the membrane structure was discussed

'The Role of the Grain Boundary on the Resistivity of Pb(Fe1/2Nb1/2)O3 at Room Temperature

2002 ◽  
Vol 718 ◽  
Author(s):  
Sang-Bop Lee ◽  
Kwang-Ho Lee ◽  
Hwan Kim
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Sintered Specimen ◽  
Room Temperature Resistivity ◽  
Boundary Properties ◽  
Order Of Magnitude ◽  
The Difference ◽  
Fe Reduction ◽  
Temperature Resistivity

AbstractThe effect of changing sintering temperature on the grain boundary properties and the room temperature resistivity (ρRT) of Pb(Fe1/2Nb1/2)O3 (PFN) was investigated. Monitering the temperature dependence of resistivity showed that the ρRT's of 1050°C and 1150°C-sintered specimen were 1011ΩEcm and 104ΩEcm respectively, but the resistivity above 300°C became nearly identical. The previous model, that the low resistivity of PFN is due to the electron hopping between Fe2+ and Fe3+ driven by the reduction of PFN, couldn't explain this phenomenon, and the reconsideration of the Fe reduction revealed that the difference of electron concentration between the 1050°C and 1150°C-sintered specimen couldn't exceed one order of magnitude. The role of the grain boundary was introduced in order to account for this phenomenon.

Carbon Doping into GaAs Using Low-Energy Hydrocarbon Ions

1998 ◽  
Vol 510 ◽  
Author(s):  
Hirokazu Sanpei ◽  
Takayuki Shima ◽  
Yunosuke Makita ◽  
Shinji Kimura ◽  
Yasuhiro Fukuzawa ◽  
...  
Keyword(s):  
Low Temperature ◽  
Room Temperature ◽  
Molecular Beam ◽  
Ion Beam ◽  
Low Energy ◽  
Carbon Doping ◽  
Co Doping ◽  
Hall Effect Measurements ◽  
Low Temperature Photoluminescence

AbstractThe role of hydrogen (H) in carbon (C)-doped GaAs was examined by co-doping of C and H atoms using low-energy hydrocarbon (CH+ and CH3+) ions. Experiments were carried out using the combined ion beam and molecular beam epitaxy (CIBMBE) system. Samples were characterized by low-temperature photoluminescence at 2K and Hall effect measurements at room temperature. Results show that incorporated C atoms are optically and electrically activated as acceptors even by hydrocarbon ion impingement. The effect of H incorporation was found to be noticeable when impinged current density of CH3+ ion beam is high that produces equivalent net hole carrier concentration greater than ∼1018 cm−3

Modification of tyrosine residues of tomato pectin esterase

1983 ◽  
Vol 48 (2) ◽  
pp. 668-671 ◽  
Author(s):  
Oskar Markovič
Keyword(s):  
Enzyme Molecule ◽  
Original Activity ◽  
Ph Titration ◽  
Tyrosine Residues ◽  
Irreversible Inhibition ◽  
Molar Excess ◽  
Catalytic Function ◽  
Pectin Esterase ◽  
The Difference

Selective acetylation of tyrosine residues in tomato pectin esterase with an 80 molar excess of n-acetylimidazole reduced the activity of the enzyme to 50%. Deacetylation with hydroxylamine restored the original activity of the enzyme. The difference in absorptivities at 278 nm showed that 2 tyrosine residues of the enzyme had been acetylated. Spectrophotometric pH-titration of native pectin esterase revealed that 2 of the 12 tyrosine residues in the enzyme molecule were ionized at pH 9.3-9.5, and the remaining 10 residues at pH > 10.5. Acetylation of the pectin esterase with acetanhydride resulted in an irreversible inhibition of the enzyme. Nitration of the enzyme with tetranitromethane also suggested a role of the tyrosine residues in the catalytic function of the enzyme. However, 10 min after the start of the nitration precipitation set in.

Role of the wrist cuff in forearm plethysmography

1991 ◽  
Vol 80 (5) ◽  
pp. 413-417 ◽  
Author(s):  
Jacques Lenders ◽  
Geert-Jan Janssen ◽  
Paul Smits ◽  
Theo Thien
Keyword(s):  
Blood Flow ◽  
Room Temperature ◽  
Forearm Blood Flow ◽  
Large Range ◽  
Cuff Pressure ◽  
Venous Pressure ◽  
Systolic Pressure ◽  
Ambient Temperatures ◽  
The Difference

1. To determine whether a wrist cuff is necessary to measure the forearm blood flow correctly, we studied the effects of wrist cuff inflation to supra-venous and supra-systolic pressure values over a large range of forearm blood flow values: in the basal state, during post-occlusive hyperaemia of the hand, and during heating of the hand with warm air. Eleven healthy men participated, and the study was carried out at two different ambient temperatures of 20 and 25°C. 2. In the basal state, the measured forearm blood flow was lowest with the wrist cuff at supra-systolic pressure. With the wrist cuff at supra-venous pressure the forearm blood flow was also lower than with an uninflated cuff, but only significantly so when the basal forearm blood flow was higher (at a room temperature of 25°C). 3. During post-occlusive hyperaemia, inflating the wrist cuff to supra-systolic pressure produced the lowest forearm blood flow value at both room temperatures. In addition, with the wrist cuff at supra-venous pressure, forearm blood flow values were lower than with the uninflated cuff, but the supra-venous cuff pressure was clearly less efficient in excluding the hand blood flow than the supra-systolic cuff pressure. 4. During heating of the hand, both supra-systolic and supra-venous cuff pressures were effective in excluding the hand blood flow at both room temperatures. The forearm blood flow measured with the wrist cuff at supra-systolic pressure was lower than that measured with the wrist cuff at supra-venous pressure, but the difference was only significant at a room temperature of 20°C. 5. In conclusion, we have demonstrated that a wrist cuff at supra-systolic pressure is most appropriate for the exclusion of the hand circulation in order to measure the forearm blood flow correctly.

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