Search results for "Electrophoresi"
showing 10 items of 1009 documents
On the electrophoretic mobility of isolated colloidal spheres
2004
We studied the electrophoretic mobility μ of highly charged colloidal spheres in very dilute low salt aqueous suspension. We combined experiments on individual particles and ensemble averaged measurements. In both cases μ was observed to be independent of particle size and surface chemistry. Corresponding effective charges Zμ*, however, scaled with the ratio of particle size to Bjerrum length λB: Zμ* = Aa/λB with a coefficient . Our results are discussed in comparison to other charge determination experiments and charge renormalization theory and with respect to the issue of charge polydispersity.
Convective electrodiffusion processes through graft-modified charged porous membranes
1999
Convective diffusion and electrophoresis across a charged porous membrane showing variable permeability properties were studied. The membrane used was prepared by grafting poly(acrylic acid) (PAA) onto a porous polyvinylidene fluoride (PVDF) membrane. The degree of grafting was selected to be relatively low, 18 wt%, to compromise between the ion selectivity and hydraulic permeability of the membrane. The possible electric field induced effects on the membrane permselectivity were examined after the membrane had been characterized by convective diffusion and concentration cell potential measurements. The measured electrophoresis data, however, could be modelled using the extended Teorell–Mey…
Separation of chelating agents as copper complexes by capillary zone electrophoresis using quaternary ammonium bromides as additives in N-methylforma…
2006
This study presents the use of quaternary ammonium bromides as additives in N-methylformamide (NMF) for the separation and quantification of chelating agents as copper complexes by capillary zone electrophoresis (CZE). The new quaternary ammonium bromides were synthesized in our laboratory and used for the first time for CZE applications performed in NMF media. The methods were developed and optimized for determination of six chelating agents (trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CDTA), diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetraacetic acid (EDTA), N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid (HEDTA), nitrilotriacetic acid (NTA) and trieth…
Nonlinear hairy layer theory of electrophoretic fingerprinting applied to consecutive layer by layer polyelectrolyte adsorption onto charged polystyr…
1997
The consecutive layer-by-layer adsorption of poly(allylamine hydrochloride) (PAH) and poly(styrenesulfonate) (PSS) on colloidal charged latex particles is investigated by measuring the electrophoretic mobility as a function of pH and ionic strength over a broad range (electrophoretic fingerprinting). Meaningful interpretation of the data required the development of a nonlinear approach to hairy particle electrophoresis including dissociation, adsorption, and association. Steric and electrostatic exclusion of mobile ions from the hairy layer has been considered. Also, the surface conductivity correction is extended to the case of charged hairy layer particles. We deposited up to three polyel…
Comparative analysis of short tandem repeats and single nucleotide polymorphisms on the Y-chromosome in Germans, Chinese and Thais.
2003
We have typed genomic DNA samples from 95 individuals from Western Germany, 78 individuals from Bangkok/Thailand and 56 individuals from Chengdu/China for 11 Y-chromosomal diallelic polymorphisms and eight short tandem repeat (STR) systems. For single nucleotide polymorphism (SNP) analysis, a rapid method was applied using the single base extension technology (minisequencing) in combination with capillary electrophoresis. PCR products for SRY-8299, Tat, SRY2627, 92R7, SRY1532, M9, M13, M17/M19 and M20 were pooled and used as templates for the commercially available SNaPshot kit. In addition to these ten SNPs we also tested the Y-chromosomal diallelic Alu repeat insertion DYS287 (YAP) by aga…
Methodical Studies in the Separation of Chlorophyll-Protein Complexes by Polyacrylamide Gel Electrophoresis
1980
Summary Chlorophyll-protein complexes from thylakoids of Sinapis alba plants were separated, using Tris-HCl and Tris-borate buffer in the sodium dodecyl sulphate acrylamide gel electrophoresis. In the electrophoretogram with Tris-borate buffer, 6 bands could be characterized in the gel pattern. In addition to the three major green zones (P-700-chlorophyll a-protein, light-harvesting chlorophyll a/b-protein, free pigment zone), which were also observed in experiments with the Tris-HC1 buffer, three further bands (LHCP 1 , LHCP 2 , CPa) were electrophoretically separated. An elongation of the electrophoretical period resulted especially in a decrease of the proportion of the light-harvesting …
Chlorophyll-Protein Complexes of Chlorella fusca
1980
Chlorophyll-protein complexes from thylakoids of the normal type and two mutants of Chlorella fusca were separated using sodium dodecyl sulfate acrylamide gel electrophoresis (PAGE). The properties of the chlorophyll-protein complexes of the three strains of Chlorella were compared. Standard curves were set up for the characterization of the chlorophyll-proteins. In every electrophoretic separation of chlorophyll-protein complexes, a certain amount of pigment is separated from the protein. We tried to keep that amount as low as possible by mild solubilization and by working in low temperature. Under these conditions, we obtained several new chlorophyll-proteins in addition to the P-700-chl…
The negatively charged amino acids in the lumenal loop influence the pigment binding and conformation of the major light-harvesting chlorophyll a/b c…
2008
AbstractThe major chlorophyll (Chl) a/b complexes of photosystem II (LHCIIb), in addition to their primary light-harvesting function, play key roles in the organization of the granal ultrastructure of the thylakoid membranes and in various regulatory processes. These functions depend on the structural stability and flexibility of the complexes. The lumenal side of LHCIIb is exposed to broadly variable pH environments, due to the build-up and decay of the pH gradient during photosynthesis. Therefore, the negatively charged amino acids in the lumenal loop might be of paramount importance for adjusting the structure and functions of LHCIIb. In order to clarify the structural roles of these res…
Carotenoid binding sites in LHCIIb
2000
The major light-harvesting complex of photosystem II can be reconstituted in vitro from its bacterially expressed apoprotein with chlorophylls a and b and neoxanthin, violaxanthin, lutein, or zeaxanthin as the only xanthophyll. Reconstitution of these one-carotenoid complexes requires low-stringency conditions during complex formation and isolation. Neoxanthin complexes (containing 30–50% of the all-trans isomer) disintegrate during electrophoresis, exhibit a largely reduced resistance against proteolytic attack; in addition, energy transfer from Chl b to Chl a is easily disrupted at elevated temperature. Complexes reconstituted in the presence of either zeaxanthin or lutein contain nearly …
The Folding State of the Lumenal Loop Determines the Thermal Stability of Light-Harvesting Chlorophyll a/b Protein
2004
The major light-harvesting protein of photosystem II (LHCIIb) is the most abundant chlorophyll-binding protein in the thylakoid membrane. It contains three membrane-spanning alpha helices; the first and third one closely interact with each other to form a super helix, and all three helices bind most of the pigment cofactors. The protein loop domains connecting the alpha helices also play an important role in stabilizing the LHCIIb structure. Single amino acid exchanges in either loop were found to be sufficient to significantly destabilize the complex assembled in vitro [Heinemann, B., and Paulsen, H. (1999) Biochemistry 38, 14088-14093. Mick, V., Eggert, K., Heinemann, B., Geister, S., and…