Structure of bacteriorhodopsin in the acidified membrane and at high ionic strength: resonance Raman study

1985 ◽  
Vol 63 (7) ◽  
pp. 2012-2017 ◽  
Author(s):  
G. Massig ◽  
M. Stockburger ◽  
Th. Alshuth
Keyword(s):  
Ionic Strength ◽  
Resonance Raman ◽  
Ion Pair ◽  
High Ionic Strength ◽  
Original Structure ◽  
Water Molecules ◽  
Native State ◽  
Surrounding Water ◽  
Acidic Form ◽  
Raman Study

Resonance Raman (RR) spectra of the retinylidene Schiffs base (SB) chromophore of bacteriorhodopsin (BR) were obtained from purple membrane (PM) suspensions of Halobacteriumhalobium in three different equilibrium states: (1) the native state at neutral pH; (2) BR-605, the acidified membrane at pH 2; (3) BR-565(Cl−) or BR-545 (F−), at low pH and high ionic strength. In the native state the retinyl chromophore is stabilized by an ion-pair complex of the protonated SB group with a negative carboxylate counterion (A−) of the protein, giving [Formula: see text]. In the acidic form, BR-605, it is inferred from the RR spectra that the chromophore is immobilized. This is ascribed to a breakdown of the ionic interaction by protonation of A−. In the two (3) forms the RR spectra show that the original structure of the chromophore in the native state is reestablished, which is attributed to the formation of [Formula: see text] complexes with the anions. It thus turns out from RR spectroscopic evidence that the retinyl chromophore in BR is largely governed by the [Formula: see text] ion-pair formation, which is stabilized by surrounding water molecules.

scholarly journals High salt compatible oxyanion receptors by dual ion imprinting

2020 ◽  
Vol 11 (16) ◽  
pp. 4246-4250 ◽  
Author(s):  
Sudhirkumar Shinde ◽  
Mona Mansour ◽  
Anil Incel ◽  
Liliia Mavliutova ◽  
Celina Wierzbicka ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Ion Pair ◽  
High Ionic Strength ◽  
High Salt ◽  
Ion Uptake ◽  
Ion Imprinting

Imprinting of an ion-pair in presence of mutually compatible anion and cation host monomers leads to polymers showing enhanced ion uptake in competitive high ionic strength buffers.

scholarly journals Parthenogenesis in Xenopus eggs requires centrosomal integrity.

1990 ◽  
Vol 110 (2) ◽  
pp. 405-415 ◽  
Author(s):  
C Klotz ◽  
M C Dabauvalle ◽  
M Paintrand ◽  
T Weber ◽  
M Bornens ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Protein Unfolding ◽  
Protein Structures ◽  
High Ionic Strength ◽  
Native State ◽  
Apparent Paradox ◽  
Complete Protein ◽  
Duplication Cycle ◽  
Structure And Activity

Xenopus eggs are laid arrested at second metaphase of meiosis lacking a functional centrosome. Upon fertilization, the sperm provides the active centrosome that is required for cleavage to occur. The injection of purified centrosomes mimics fertilization and leads to tadpole formation (parthenogenesis). In this work we show that the parthenogenetic activity of centrosomes is inactivated by urea concentrations higher than 2 M. The loss of activity is correlated with a progressive destruction of the centriolar cylinder and extraction of proteins. This shows that centrosomes are relatively sensitive to urea since complete protein unfolding and solubilization of proteins normally occurs at urea concentrations as high as 8-10 M. When present, the parthenogenetic activity is always associated with a pelletable fraction showing that it cannot be solubilized by urea. The parthenogenetic activity is progressively inactivated by salt concentrations higher than 2 M (NaCl or KCl). However, only a few proteins are extracted by these treatments and the centrosome ultrastructure is not affected. This shows that both parthenogenetic activity and centrosomal structure are resistant to relatively high ionic strength. Indeed, most protein structures held by electrostatic forces are dissociated by 2 M salt. The loss of parthenogenetic activity produced at higher salt concentrations, while the structure of the centrosome is unaffected, is an apparent paradox. We interpret this result as meaning that the native state of centrosomes is held together by forces that favor functional denaturation by high ionic strength. The respective effects of urea and salts on centrosomal structure and activity suggest that the centrosome is mainly held together by hydrogen and hydrophobic bonds. The in vitro microtubule nucleating activity of centrosomes can be inactivated at salt or urea concentrations that do not affect the parthenogenetic activity. Since egg cleavage requires the formation of microtubule asters, we conclude that the extracted or denatured microtubule nucleating activity of centrosomes can be complemented by components present in the egg cytoplasm. Both parthenogenetic and microtubule nucleating activities are abolished by protease treatments but resist nuclease action. Since we find no RNA in centrosomes treated by RNase, they probably do not contain a protected RNA. Taken together, these results are consistent with the idea that the whole or part of the centrosome structure acts as a seed to start the centrosome duplication cycle in Xenopus eggs.

Time-Resolved Resonance Raman Study of the Rate of Separation of a Geminate Ion Pair into Free Ions in a Medium Polarity Solvent

1994 ◽  
Vol 116 (20) ◽  
pp. 9182-9186 ◽  
Author(s):  
Eric Vauthey ◽  
Anthony W. Parker ◽  
Bohdana Nohova ◽  
David Phillips
Keyword(s):  
Resonance Raman ◽  
Ion Pair ◽  
Time Resolved ◽  
Medium Polarity ◽  
Free Ions ◽  
Raman Study

Importance of Protease Inhibition in Studies on Purified Factor VIII (Antihaemophilic Factor)

1976 ◽  
Vol 35 (01) ◽  
pp. 186-190 ◽  
Author(s):  
Eugen A. Beck ◽  
Peter Bachmann ◽  
Peter Barbier ◽  
Miha Furlan
Keyword(s):  
Ionic Strength ◽  
Factor Viii ◽  
Gel Filtration ◽  
High Ionic Strength ◽  
Procoagulant Activity ◽  
Carrier Protein ◽  
Protease Inhibition ◽  
Functional Sites ◽  
Molecular Weight Peak ◽  
Von Willebrand

SummaryAccording to some authors factor VIII procoagulant activity may be dissociable from carrier protein (MW~ 2 × 106) by agarose gel filtration, e.g. at high ionic strength. We were able to reproduce this phenomenon. However, addition of protease inhibitor (Trasylol) prevented the appearance of low molecular weight peak of factor VIII procoagulant activity both at high ionic strength and elevated temperature (37°C). We conclude from our results that procoagulant activity and carrier protein (von Willebrand factor, factor VIII antigen) are closely associated functional sites of native factor VIII macro molecule. Consequently, proteolytic degradation should be avoided in functional and structural studies on factor VIII and especially in preparing factor VIII concentrate for therapeutic use.

THE RELATIVE DISTRIBUTION OF THYROXINE, TRIIODOTHYRONINE AND 3,3′,5′-(REVERSE)-TRIIODOTHYRONINE IN VARIOUS FRACTIONS OF THYROGLOBULIN

1978 ◽  
Vol 88 (2) ◽  
pp. 298-305 ◽  
Author(s):  
Peter Laurberg
Keyword(s):  
Ionic Strength ◽  
Guinea Pig ◽  
Sucrose Gradient ◽  
Deae Cellulose ◽  
High Ionic Strength ◽  
Relative Distribution ◽  
Thyroid Extract ◽  
Reverse Triiodothyronine ◽  
Thyroid Secretion ◽  
Stable Iodine

ABSTRACT Thyroglobulin fractions rich and poor in new thyroglobulin were separated by means of DEAE-cellulose chromatography of dog thyroid extracts and by zonal ultracentrifugation in a sucrose gradient of guinea pig thyroid extract incubated at low temperature. The distribution of thyroxine, triiodothyronine and 3,3′,5′-(reverse)-triiodothyronine in hydrolysates of the different fractions was estimated by radioimmunoassays. Following DEAE-cellulose chromatography there was a small but statistically significant increase in the T4/T3 ratio in thyroglobulin fractions eluted at high ionic strength - that is fractions relatively rich in stable iodine but poor in fresh thyroglobulin. There were no differences in the T4/rT3 ratios between the different fractions. The ratios between iodothyronines were almost identical in the various thyroglobulin fractions following zonal ultracentrifugation in a sucrose gradient of cold treated guinea pig thyroid extract. These findings lend no support to the possibility that a relatively high content of triiodothyronines in freshly synthesized thyroglobulin modulates the thyroid secretion towards a preferential secretion of triiodothyronine and 3,3′,5′-(reverse)-triiodothyronine at the expense of the secretion of thyroxine.

A pH-dependent resonance raman study on blue copper site of cucumber stellacyanin and its GLN→MET variant

1997 ◽  
Vol 67 (1-4) ◽  
pp. 49
Author(s):  
G. Fraczkiewicz ◽  
A.R. Nersissian ◽  
J.P. Hart ◽  
J.S. Valentine ◽  
R.S. Czernuszewicz
Keyword(s):  
Resonance Raman ◽  
Blue Copper ◽  
Copper Site ◽  
Raman Study ◽  
Ph Dependent

scholarly journals Structure of aqueous sodium acetate solutions by X-Ray scattering and density functional theory

2020 ◽  
Vol 92 (10) ◽  
pp. 1627-1641
Author(s):  
Guangguo Wang ◽  
Yongquan Zhou ◽  
He Lin ◽  
Zhuanfang Jing ◽  
Hongyan Liu ◽  
...  
Keyword(s):  
Sodium Acetate ◽  
Density Functional ◽  
Hydration Shell ◽  
Ion Pair ◽  
Water Molecules ◽  
Sodium Acetate Solution ◽  
Acetate Solution ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

AbstractThe structure of aq. sodium acetate solution (CH3COONa, NaOAc) was studied by X-ray scattering and density function theory (DFT). For the first hydrated layer of Na+, coordination number (CN) between Na+ and O(W, I) decreases from 5.02 ± 0.85 at 0.976 mol/L to 3.62 ± 1.21 at 4.453 mol/L. The hydration of carbonyl oxygen (OC) and hydroxyl oxygen (OOC) of CH3COO− were investigated separately and the OC shows a stronger hydration bonds comparing with OOC. With concentrations increasing, the hydration shell structures of CH3COO− are not affected by the presence of large number of ions, each CH3COO− group binds about 6.23 ± 2.01 to 7.35 ± 1.73 water molecules, which indicates a relatively strong interaction between CH3COO− and water molecules. The larger uncertainty of the CN of Na+ and OC(OOC) reflects the relative looseness of Na-OC and Na-OOC ion pairs in aq. NaOAc solutions, even at the highest concentration (4.453 mol/L), suggesting the lack of contact ion pair (CIP) formation. In aq. NaOAc solutions, the so called “structure breaking” property of Na+ and CH3COO− become effective only for the second hydration sphere of bulk water. The DFT calculations of CH3COONa (H2O)n=5–7 clusters suggest that the solvent-shared ion pair (SIP) structures appear at n = 6 and become dominant at n = 7, which is well consistent with the result from X-ray scattering.

scholarly journals Origin and control of ionic hydration patterns in nanopores

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Miraslau L. Barabash ◽  
William A. T. Gibby ◽  
Carlo Guardiani ◽  
Alex Smolyanitsky ◽  
Dmitry G. Luchinsky ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Distribution Functions ◽  
Water Molecules ◽  
Surrounding Water ◽  
Ionic Hydration ◽  
Hydration Shells ◽  
Water Layers ◽  
Dynamics Simulations ◽  
And Control

AbstractIn order to permeate a nanopore, an ion must overcome a dehydration energy barrier caused by the redistribution of surrounding water molecules. The redistribution is inhomogeneous, anisotropic and strongly position-dependent, resulting in complex patterns that are routinely observed in molecular dynamics simulations. Here, we study the physical origin of these patterns and of how they can be predicted and controlled. We introduce an analytic model able to predict the patterns in a graphene nanopore in terms of experimentally accessible radial distribution functions, giving results that agree well with molecular dynamics simulations. The patterns are attributable to a complex interplay of ionic hydration shells with water layers adjacent to the graphene membrane and with the hydration cloud of the nanopore rim atoms, and we discuss ways of controlling them. Our findings pave the way to designing required transport properties into nanoionic devices by optimising the structure of the hydration patterns.

scholarly journals Kaolin based protective barrier in municipal landfills against adverse chemo-mechanical loadings

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Partha Das ◽  
Tadikonda Venkata Bharat
Keyword(s):  
Ionic Strength ◽  
High Ionic Strength ◽  
The Self ◽  
Design Parameters ◽  
Layered System ◽  
Geosynthetic Clay Liners ◽  
Clay Liners ◽  
Landfill Liner ◽  
First Time ◽  
Applied Stresses

AbstractIn this work, we assess the self-sealing and swelling ability of the compacted granular bentonite (GB) under an inorganic salt environment and induced overburden stresses from the landfill waste. The laboratory permeation tests with high ionic strength salt solutions reveal that the GB fails to seal and exhibits a significant mechanical collapse under different applied stresses. The applicability of GB in the form of geosynthetic clay liners as the bottom liner facilities in landfills that produce high ionic strength salt leachates, therefore, remains a serious concern. We propose an additional barrier system based on kaolin, for the first time, to address this problem. The proposed kaolin-GB layered system performs satisfactorily in terms of its sealing and swelling ability even in adverse saline conditions and low overburden stresses. The kaolin improves the osmotic efficiency of the self and also helps the underlying GB layer to seal the inter-granular voids. The estimated design parameters by through-diffusion test suggest that the kaolin-GB layered system effectively attenuates the permeant flux and suitable as a landfill liner.

scholarly journals High ionic strength dissociation assay (HISDA) for high drug tolerant immunogenicity testing

Bioanalysis ◽  
2020 ◽  
Author(s):  
Gregor Jordan ◽  
Alexander Pöhler ◽  
Florence Guilhot ◽  
Meike Zaspel ◽  
Roland F Staack
Keyword(s):  
Ionic Strength ◽  
Acid Treatment ◽  
Structural Integrity ◽  
Drug Tolerance ◽  
High Ionic Strength ◽  
Acid Dissociation ◽  
High Drug ◽  
Overnight Incubation ◽  
Antidrug Antibody ◽  
High Doses

Aim: Antidrug antibody (ADA) assessment may be challenged in studies that involve the administration of high doses of biotherapeutics and/or with long half-lives. In such cases, ADA assays with optimized drug tolerance are desired. Material & Methods: We evaluated the use of MgCl2 to develop high ionic strength dissociation assays in two investigational examples (bridging enzyme-linked immunosorbent ADA assays) to attain high drug tolerance while maintaining best possible structural integrity of ADAs. Results: Both ADA-bridging assays treated with MgCl2 showed improved drug tolerance and higher signal-to-blank values compared with overnight incubation or acid treatment. Conclusion: The use of MgCl2 treatment in ADA-bridging assays provides a sensitive, drug tolerant and easy-to-use alternative in cases where acid dissociation is not possible or unwanted.

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