A novel method of determination of the internal enzyme distribution within porous solid supports and the deactivation rate constant

1986 ◽  
Vol 28 (4) ◽  
pp. 486-493 ◽  
Author(s):  
D. D. Do ◽  
M. M. Hossain
Keyword(s):  
Rate Constant ◽  
Porous Solid ◽  
Solid Supports ◽  
Deactivation Rate ◽  
Method Of Determination ◽  
Enzyme Distribution ◽  
Deactivation Rate Constant ◽  
Novel Method

Atomic Layer Deposition for Improved Stability of Catalysts for the Conversion of Biomass to Chemicals and Fuels

2011 ◽  
Vol 1366 ◽  
Author(s):  
Monika K. Wiedmann ◽  
Yomaira J. Pagan-Torres ◽  
Mark H. Tucker ◽  
James A. Dumesic ◽  
T. F. Kuech
Keyword(s):  
Atomic Layer Deposition ◽  
Metal Oxides ◽  
Rate Constant ◽  
Flow Reactor ◽  
Atomic Layer ◽  
Deactivation Rate ◽  
Layer Deposition ◽  
Improved Stability ◽  
Deactivation Rate Constant ◽  
Acid Catalyzed

ABSTRACTAtomic layer deposition (ALD) has been used to coat SBA-15 and functionalized SBA-15 with various metal oxides. Use of SBA-15 coated with 4-10 ALD cycles of titania, alumina, niobia, or zirconia in the acid-catalyzed dehydration of fructose to 5-hydroxymethylfurfural (HMF) resulted in 24-57% conversion, with 0-22% selectivity, at 130 °C with 2 wt % fructose in 4:1 THF:H2O. Propylsulfonic acid functionalized SBA-15 (SBA-15-PrSO3H) had a 25% conversion and 48% selectivity for HMF under the same conditions. SBA-15-PrSO3H was also coated with 2 ALD cycles of titania followed by 8 ALD cycles silica. The deactivation rate constant for SBA-15-PrSO3H was 2.7 x 10-2 h-1 for the dehydration of fructose to HMF in a flow reactor at 130 °C with a feed of 2 wt % fructose in 4:1 THF:H2O. In comparison, the deactivation rate constant for the ALD coated SBA-15-PrSO3H-ALD was 7.9 x 10-3 h-1.

A novel method of determination of wire lag for enhanced profile accuracy in WEDM

2011 ◽  
Vol 35 (2) ◽  
pp. 339-347 ◽  
Author(s):  
S. Sarkar ◽  
M. Sekh ◽  
S. Mitra ◽  
B. Bhattacharyya
Keyword(s):  
Method Of Determination ◽  
Novel Method ◽  
Profile Accuracy

Study on the Spectrophotometric Determination of Trace Cadmium after Flotation Separation with Ternary Association Complex System

2011 ◽  
Vol 356-360 ◽  
pp. 1234-1237
Author(s):  
Xin Rong Wen ◽  
Chang Qing Tu
Keyword(s):  
Complex System ◽  
Trimethyl Ammonium Chloride ◽  
Experimental Conditions ◽  
Method Of Determination ◽  
Quantitative Separation ◽  
Novel Method ◽  
Solid Phases ◽  
Trace Cadmium ◽  
Association Complex

The paper presents a novel method for the flotation separation of Cd2+with ternary association complex system prior to the determination by spectrophotometry. The effects of different parameters,such as the dosages of KI and octadecyl trimethyl ammonium chloride (OTMAC),various salts and acidity etc. on the flotation yield of Cd2+have been investigated to select the experimental conditions. The possible flotation mechanism of Cd2+was discussed.The results showed that by controlling pH2.0,in the presence of 1.0g (NH4)2SO4, when the dosage of 0.1 mol•L-1KI solution was 2.00 mL and 0.01 mol•L-1OTMAC solution was 2.00 mL respectively, the water-insoluble ternary association complex of (OTMAC)2(CdI4) which produced by Cd2+and I-,OTMAC cation (OTMAC+) floated above water phase and liquid-solid phases were formed with clear interface,while Mn2+, Ni2+,Co2+, Zn2+and Al3+could not be floated,so Cd2+was floated quantitatively at pH2.0. Thereby, the quantitative separation of Cd2+from the above metal ions could be achieved.A new method of determination of trace cadmium by flotation separation was established.The proposed method has been successfully applied to the determination of Cd2+in the sample of synthetic water and the flotation yield was 97.2%~108.7%.

scholarly journals The role of the C-terminal tail of flavocytochrome b2

1989 ◽  
Vol 263 (3) ◽  
pp. 849-853 ◽  
Author(s):  
S A White ◽  
M T Black ◽  
G A Reid ◽  
S K Chapman
Keyword(s):  
Rate Constant ◽  
Structural Integrity ◽  
Lactate Concentration ◽  
Wild Type ◽  
Wild Type Enzyme ◽  
Original Activity ◽  
First Order ◽  
Flavocytochrome B2 ◽  
Deactivation Rate ◽  
Deactivation Rate Constant

A flavocytochrome b2 (L-lactate dehydrogenase) mutant was constructed in which the C-terminal tail (23 amino acid residues) had been deleted (Gly-489→Stop). This tail appears to form many intersubunit contacts in the tetrameric wild-type protein, and it was expected that its removal might lead to the formation of monomeric flavocytochrome b2. The isolated tail-deleted mutant enzyme (TD-b2), however, was found to be tetrameric (Mr 220,000). TD-b2 shows Km and kcat. values (at 25 degrees C and pH 7.5) of 0.96 +/- 0.06 mM and 165 +/- 6 s-1 respectively compared with 0.49 +/- 0.04 mM and 200 +/- 10 s-1 for the wild-type enzyme. The kinetic isotope effect with [2-2H]lactate as substrate seen for TD-b2, with ferricyanide as electron acceptor, was essentially the same as that observed for the wild-type enzyme. TD-b2 exhibited loss of activity during turnover in a biphasic process. The rate of the faster of the two phases was dependent on L-lactate concentration and at saturating concentrations showed a first-order deactivation rate constant, kf(deact.), of 0.029 s-1 (at 25 degrees C and pH 7.5). The slower phase, however, was independent of L-lactate concentration and gave a first-order deactivation rate constant, ks(deact.), of 0.01 s-1 (at 25 degrees C and pH 7.5). This slower phase was found to correlate with dissociation of FMN, which is one of the prosthetic groups of the enzyme. Thus fully deactivated TD-b2, which was also tetrameric, was found to be completely devoid of FMN. Much of the original activity of TD-b2 could be recovered by re-incorporation of FMN. Thus the C-terminal tail of flavocytochrome b2 appears to be required for the structural integrity of the enzyme around the flavin active site even though the two are well separated in space.

Predictive modeling of the total deactivation rate constant of singlet oxygen by heterocyclic compounds

2009 ◽  
Vol 28 (1) ◽  
pp. 12-19 ◽  
Author(s):  
Andrew G. Mercader ◽  
Pablo R. Duchowicz ◽  
Francisco M. Fernández ◽  
Eduardo A. Castro ◽  
Franco M. Cabrerizo ◽  
...  
Keyword(s):  
Singlet Oxygen ◽  
Rate Constant ◽  
Predictive Modeling ◽  
Heterocyclic Compounds ◽  
Deactivation Rate ◽  
Deactivation Rate Constant
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