The pH dependence of the thermodynamics of the interaction of diazepam with human serum albumin.

Janssen, Lambert H.M.; Dröge, J. H. M.; Durlinger, F. C. J.; Fruytier, F. J.

doi:10.1016/s0021-9258(17)39047-6

Cited by 9 publications

(2 citation statements)

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“…Flow microcalorimetry has found a variety of applications, such as the study of the energetics and kinetics of chemical reactions [1][2][3], the determination of enthalpies of dilution [4][5][6][7] and mixture [8][9][10][11][12], heat capacities of liquids and solutions [13], enthalpimetric titrations [14], the binding of substrates to proteins [15,16], or the monitoring of enzymatic activity [17][18][19]. Provided that the reaction duration is compatible with the residence time of the reaction mixture in the calorimetric cell, secondary heat effects associated with the combination of the two reagent flows (e.g., enthalpy of mixing of two dissimilar buffer systems) or with heat dissipation by friction due to the use of solutions of different viscosity (e.g., viscous sucrose solutions and water) can be controlled or accounted for, and efficient mixing of the reactants is 1 Author to whom any correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

“…Here we describe the set-up and test of a modified version of a LKB 10700-1 flow microcalorimeter, which comprised the implementation of a computer-controlled data acquisition and handling system and the entire replacement of the ancillary equipment for pumping, pre-thermostatization, thermopile output measurement and electrical calibration. A new experimental protocol, in which the dilution and 4) thermostated air jacket, (5) air thermostat, (6) fan, (7) pre-thermostatic bath, (8) cooling coil, (9) thermopiles, (10) nanovoltmeter used to monitor the output of the thermopiles, (11) multi-channel peristaltic pump, (12,13) tubes leading to the mixing cell, (14) tube leading to the reference cell, (15) electrical resistance used for calibration, (16) multimeter of the calibration circuit, (17) power supply of the calibration circuit, (18) precision thermistor used to measure the temperature of the calorimeter proper, (19) computer for experiment control and data acquisition. calibration measurements were combined in a single run, with significant economy in experiment time, was also tested.…”

Section: Introductionmentioning

confidence: 99%

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A calorimetric system based on the LKB 10700-1 flow microcalorimeter

Leskiv¹,

Bernardes²,

Piedade

2009

Meas. Sci. Technol.

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An electrically calibrated and computer-controlled apparatus based on the LKB 10700-1 flow microcalorimeter was set up and tested by determining the enthalpies of dilution of aqueous solutions of sucrose and HCl at 298.15 K. The obtained results are in good agreement with the corresponding reference values recommended in the literature. The quality of the calorimetric signal in terms of noise, linearity and baseline drift, and the instrument time constant were analyzed. Also investigated were the influences of the flow rate and of the viscosity of the calorimetric liquid on the position of the baseline. The new calibration system enables powers ∼25 times smaller than those possible with the original one to be released inside the calorimetric cells. Electrical calibrations carried out with water as the sole calorimetric liquid indicated that the precision of the calibration constant, ε, quickly improved from ∼9% to ∼0.4% with the increase of the input power, P, from ∼2 µW to ∼50 µW, and stabilized at ∼0.1% for P ⩾ 100 µW. The calibration constant was also found to linearly increase with the flow rate of the calorimetric liquid and to vary by less than 1% over a period of eight months under similar experimental conditions. Finally a new experimental procedure for heat of dilution measurements, which combines calibration and experiment in a single run, was evaluated. This method allows a significant economy in experiment time with apparently no accuracy loss relative to the conventional procedure recommended in the literature.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A calorimetric system based on the LKB 10700-1 flow microcalorimeter

Leskiv¹,

Bernardes²,

Piedade

2009

Meas. Sci. Technol.

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Histidine146 of human serum albumin plays a prominent role at the interface of subdomains IA and IIA in allosteric ligand binding

Kaneko¹,

Chuang²,

Minomo³

et al. 2011

IUBMB Life

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SummaryFatty acids are endogenous ligands of human serum albumin (HSA) that induce conformational changes and participate in allosteric ligand binding to HSA. In a previous study, we showed that, when myristate (MYR) is present, the binding of [ 14 C]ketoprofen (KP) to subdomain IA of HSA was increased, indicating that, when MYR binds to HSA, a new binding site in formed in that region. Meanwhile, an N-B transition has been reported to increase the binding of ligands at alkaline pH when the status of albumin is the B-conformer. Six histidine single mutants of HSA, H9A, H39A, H67A, H105A, H128A and H146A were produced and photolabeled with [ 14 C]KP at pH 6.5, 7.4 and 8.2 and the role of each histidine in causing the N-B transition induced allosteric ligand binding was examined. Cyanogen bromide cleavage of the photolabeled native HSA showed that subdomain IA was the site of the allosteric binding of KP at pH 8.2. From the photolabeling results, H146 was found to play a prominent role whilst H128 played little or no role in the allosteric binding. However, the remaining 4 mutants did not show a clear photolabeling pattern that was similar to either native HSA or H146A and, as a result, no firm conclusions can be made. An additional histidine mutant, H146I, was produced to confirm the results for H146A. A similar experiment using H146I showed that a benzene ring-like structure at position 146 is required for the allosteric ligand binding to occur.

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