Reactions of sulfur dioxide with photochemically generated polypyridyl complexes of chromium(II). Calculation of the sulfur dioxide/sulfur dioxide radical anion self-exchange rate constant

1989 ◽  
Vol 28 (3) ◽  
pp. 581-584 ◽  
Author(s):  
Carol A. Simmons ◽  
Andreja Bakac ◽  
James H. Espenson
Keyword(s):  
Exchange Rate ◽  
Sulfur Dioxide ◽  
Rate Constant ◽  
Radical Anion ◽  
Polypyridyl Complexes ◽  
Exchange Rate Constant

Pressure effect on hydrogen isotope exchange kinetics in chymotrypsinogen investigated by FT-IR spectroscopy

1991 ◽  
Vol 69 (11) ◽  
pp. 1699-1704 ◽  
Author(s):  
P. T. T. Wong
Keyword(s):  
High Pressure ◽  
Exchange Rate ◽  
Rate Constant ◽  
Bound Water ◽  
Pressure Effects ◽  
Protein Molecules ◽  
Fast Exchange ◽  
Exchange Rate Constant ◽  
Hydrogen Deuterium ◽  
Exchange Kinetics

Hydrogen/deuterium (H/D) exchange rate constants in chymotrypsinogen have been determined at several pressures up to 28.9 kbar by FTIR spectroscopy. The secondary structure of the protein molecules was monitored simultaneously at the corresponding pressures by the intensity redistribution of the infrared amide I band at these pressures. As in other proteins, the labile protons on the amide groups in chymotrypsinogen can, to a good approximation, be separated into two classes, each with distinct first order H/D exchange rates constants in the time period from 10 min to ~24 h. The fast exchange rate constant increases while the slow exchange rate constant decreases with increasing pressure. The increase in the fast exchange rate constant at high pressure is largely associated with the pressure-induced unfolding of the protein molecules. At extremely high pressure (12.8 kbar), in addition to the unfolding of protein molecules, pressure induced a distortion and weakening of the hydrogen bonds of the fold protein segments also contribute to an increase in the overall H/D exchange rate. The present results confirm that when chymotrypsinogen is dissolved in D2O, a considerable amount of D2O molecules is bound to the protein molecules on the surface as well as in the interior cavities of the molecules. The H/D exchange takes place between these bound D2O and the protons in the protein molecules. The mechanism of the H/D exchange and the interior dynamics in proteins are discussed on the basis of the present results. Key words: hydrogen/deuterium exchange, exchange kinetics, rate constant, pressure effects, infrared spectroscopy, protein, conformation structure, bound water.

The Oxidation of Dithiocarbamate Anion by Substitution Inert Metal Complexes

1989 ◽  
Vol 42 (7) ◽  
pp. 1085 ◽  
Author(s):  
PJ Nichols ◽  
MW Grant
Keyword(s):  
Electron Transfer ◽  
Exchange Rate ◽  
Metal Complexes ◽  
Radical Anion ◽  
Outer Sphere ◽  
Aqueous Acetone ◽  
Kinetics Of Oxidation ◽  
Rate Determining Step ◽  
Exchange Rate Constant ◽  
Kinetics Of

The kinetics of oxidation of dithiocarbamate anions to thiuram disulfides in aqueous acetone by {Fe(CN)6}3- and 11 other substitution inert metal complexes have been investigated. Outer-sphere electron transfer, resulting in the formation of dithiocarbamate thio radicals, is the rate determining step. A Marcus cross reaction treatment allows an estimate for the redox potential for the dithiocarbamate radical/anion couple. For diethyldithiocarbamate, E �(edtc/edtc-) = 425 � 33 mV v.s.c.e. and the outer-sphere electron self-exchange rate constant is log kex = 7.0 � 0.3. A comparison with thiophenolate oxidation is also given.

Dynamic Contrast-Enhanced MRI Identifies a Distinct Group of Asymptomatic Myeloma Patients with Increased Bone Marrow Microcirculation.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 5079-5079
Author(s):  
Jens Hillengass ◽  
Christian Zechmann ◽  
Andreas Nadler ◽  
Stefan Delorme ◽  
Axel Benner ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Exchange Rate ◽  
Rate Constant ◽  
Healthy Controls ◽  
Dynamic Contrast Enhanced ◽  
Contrast Enhanced ◽  
Significant Difference ◽  
Exchange Rate Constant ◽  
Focal Pattern ◽  
Contrast Enhanced Mri

Abstract Introduction: Dynamic contrast enhanced MRI (dceMRI) is an imaging technique detecting changes in local microcirculation reflecting increased angiogenesis. The dceMRI parameters Amplitude A and exchange rate constant kep have been shown to be significantly increased in patients with active multiple myeloma (MM) compared to healthy controls and to correlate with osteolytic bone involvement and prognosis. We now compared the parameters and infiltration patterns of dceMRI in patients with monoclonal gammopathy of undetermined significance (MGUS) as well as in patients with asymptomatic MM not requiring chemotherapy (NRC-group) with those in patients with symptomatic MM requiring chemotherapy according to international standards. Methods: The NRC group contained 71 patients: 29 patients with MGUS, 39 patients with MM stage I and 3 patients with MM stage IIA according to Durie and Salmon. 24 patients had a diagnosis of a MM in stage II in progression (n = 3) or stage III (n = 21). All patients underwent standardized dceMRI with high temporal resolution (T1w-turboFLASH) of the lumbar spine before start of therapy. Color coded pharmacokinetic maps of imaged area were classified according to three distinct patterns of microcirculation: “normal” (as in healthy controls), “diffuse” or “focal”. The contrast uptake was quantified using a two compartment model with the output parameters Amplitude A and distribution constant rate kep reflecting bone marrow microcirculation. Results: 63 % of patients in the NRC group were found to have changes in the microcirculation pattern with 26 patients (37%) displaying a normal, 43 (60%) a diffuse and 2 (3%) a focal pattern. Within the NRC group 11 MGUS patients (38%) were found to have a normal pattern, 17 patients (59%) had a diffuse and 1 patient (3%) presented with a focal pattern. 79 % of patients with symptomatic MM had an abnormal microcirculation pattern with 5 (21%) MM patients showing a normal, 12 (50%) a diffuse and 7 (29%) a focal pattern. Statistical comparison did not reveal a significant difference in the total incidence between NRC and symptomatic MM group. Comparison of quantitative microcirculation parameters did not show a significant difference of Amplitude A (p=0.87) and exchange rate constant kep (p=0.3) in MGUS patients compared to patients with asymptomatic MM. Comparing the NRC group with the symptomatic myeloma group revealed a significant higher Amplitude A in the symptomatic MM group (p=0.01). There was no significant difference in exchange rate constant kep. Conclusion: Our investigations revealed a group of patients with asymptomatic myeloma and MGUS that display significant increase in bone marrow microcirculation. Our findings could be the basis for stratified treatment of patients with novel therapeutics targeting the vascular system. Prognostic implications for systemic and local development of the malignant disease are topic of current investigations.

Stable isotopic exchange rate constant between snow and liquid water

2009 ◽  
Vol 260 (1-2) ◽  
pp. 57-62 ◽  
Author(s):  
Jeonghoon Lee ◽  
Xiahong Feng ◽  
Eric S. Posmentier ◽  
Anthony M. Faiia ◽  
Susan Taylor
Keyword(s):  
Exchange Rate ◽  
Rate Constant ◽  
Liquid Water ◽  
Isotopic Exchange ◽  
Stable Isotopic ◽  
Exchange Rate Constant
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