toggle visibility Search & Display Options

Select All    Deselect All
 |   | 
Details
   print
  Records Links
Author (up) Steinhoff, H.J. openurl 
  Title A continuous wave laser T-jump apparatus and its application to chemical reactions in hemoglobin single crystals Type Journal Article
  Year 1988 Publication Journal of Biochemical and Biophysical Methods Abbreviated Journal J Biochem Biophys Methods  
  Volume 15 Issue 6 Pages 319-330  
  Keywords Animals; Chemistry; Crystallization; *Heat; *Hemoglobins; Horses/blood; *Lasers; Methemoglobin; Solutions; Thermodynamics; Thiocyanates  
  Abstract A laser temperature jump apparatus is constructed where the T-jump is achieved by means of the direct absorption of continuous laser radiation of low intensity by a solid sample. The final temperature in the irradiated volume element is reached when the absorbed radiation power equals the dissipation of heat by heat conduction. The time range from the beginning of irradiation to the stationary state depends on the geometry of the irradiated volume element and is less than 10 ms. The heating laser beam is simultaneously used to detect the relaxation to the new chemical equilibrium in the sample. Relaxation processes with relaxation rates between 10(2) s-1 and less than 10(-3) s-1 on samples with volumes less than 10(-3) mm3 may be investigated using this T-jump method. One application of this method is the determination of reaction rates of ligand reactions in hemoglobin single crystals. Rate constants obtained for the reaction of thiocyanate with crystallized horse methemoglobin are presented.  
  Address Institut fur Biophysik, Ruhr-Universitat Bochum, F.R.G  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0165-022X ISBN Medium  
  Area Expedition Conference  
  Notes PMID:3379245 Approved no  
  Call Number Equine Behaviour @ team @ Serial 3804  
Permanent link to this record
 

 
Author (up) Steinhoff, H.J.; Lieutenant, K.; Redhardt, A. openurl 
  Title Conformational transition of aquomethemoglobin: intramolecular histidine E7 binding reaction to the heme iron in the temperature range between 220 K and 295 K as seen by EPR and temperature-jump measurements Type Journal Article
  Year 1989 Publication Biochimica et Biophysica Acta Abbreviated Journal Biochim Biophys Acta  
  Volume 996 Issue 1-2 Pages 49-56  
  Keywords Animals; Electron Spin Resonance Spectroscopy; Heme; Histidine; Horses; Humans; Hydrogen-Ion Concentration; Methemoglobin/*ultrastructure; Motion; Protein Conformation; Temperature; Thermodynamics; Water  
  Abstract Temperature-dependent EPR and temperature-jump measurements have been carried out, in order to examine the high-spin to low-spin transition of aquomethemogobin (pH 6.0). Relaxation rates and equilibrium constants could be determined as a function of temperature. As a reaction mechanism for the high-spin to low-spin transition, the binding of N epsilon of His E7 to the heme iron had been proposed; the same mechanism had been suggested for the ms-effect, found in temperature-jump experiments on aquomethemoglobin. A comparison of the thermodynamic quantities, deduced form the measurements in this paper, gives evidence that indeed the same reaction is investigated in both cases. Our results and most of the findings of earlier studies on the spin-state transitions of aquomethemoglobin, using susceptibility, optical, or EPR measurements, can be explained by the transition of methemoglobin with H2O as ligand (with high-spin state at all temperatures) and methemoglobin with ligand N epsilon of His E7 (with a low-spin ground state). Thermal fluctuations of large amplitude have to be postulated for the reaction to take place, so this reaction may be understood as a probe for the study of protein dynamics.  
  Address Institut fur Biophysik, Ruhr-Universitat Bochum, F.R.G  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0006-3002 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:2544230 Approved no  
  Call Number Equine Behaviour @ team @ Serial 3803  
Permanent link to this record
 

 
Author (up) Steinhoff, H.J.; Schrader, J.; Schlitter, J. openurl 
  Title Temperature-jump studies and polarized absorption spectroscopy of methemoglobin-thiocyanate single crystals Type Journal Article
  Year 1992 Publication Biochimica et Biophysica Acta Abbreviated Journal Biochim Biophys Acta  
  Volume 1121 Issue 3 Pages 269-278  
  Keywords Animals; Crystallization; Horses; Kinetics; Methemoglobin/*chemistry; Solutions; Spectrum Analysis; Temperature; Thiocyanates/*chemistry  
  Abstract Association equilibria and association kinetics of the thiocyanate binding reaction to methemoglobin in single crystals and solution are studied using temperature-jump technique and polarized absorption spectroscopy. Different kinetic constants are found for the reaction in solution and crystal phase for the alpha- and beta-subunits of the methemoglobin tetramer. The reduction of the reactivity of the alpha- and beta-subunits in crystalline phase is 6-fold and 2.4-fold, respectively, compared to the values found in solution. The intramolecular binding reaction of the N epsilon of the distal histidine E7 which is observed in methemoglobin in solution cannot be detected in single crystals. Our results suggest that crystallization of hemoglobin has little influence on small-scale structural fluctuations which are necessary for ligands to get to the binding sites and large-scale structural motions are suppressed.  
  Address Institut fur Biophysik, Ruhr-Universitat Bochum, Germany  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0006-3002 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:1627604 Approved no  
  Call Number Equine Behaviour @ team @ Serial 3800  
Permanent link to this record
Select All    Deselect All
 |   | 
Details
   print