scholarly journals Immobilization of immunoglobulins on silica surfaces. Stability

1985 ◽  
Vol 227 (2) ◽  
pp. 363-371 ◽  
Author(s):  
U Jönsson ◽  
M Malmqvist ◽  
I Rönnberg
Keyword(s):  
Covalent Binding ◽  
Chemical Vapour ◽  
Surface Concentration ◽  
Solid Surfaces ◽  
Exchange Reactions ◽  
Covalent Bonds ◽  
Silica Surfaces ◽  
Chemically Modified Silica ◽  
Reactive Groups ◽  
Covalently Bound

The development of new immunosensors based on surface-concentration-measuring devices requires a stable and reproducible immobilization of antibodies on well-characterized solid surfaces. We here report on the immobilization of immunoglobulin G (IgG) on chemically modified silica surfaces. Such surfaces may be used in various surface-oriented analytical methods. Reactive groups were introduced to the silica surfaces by chemical-vapour deposition of silane. The surfaces were characterized by ellipsometry, contact-angle measurements and scanning electron microscopy. IgG covalently bound by the use of thiol-disulphide exchange reactions, thereby controlling the maximum number of covalent bonds to the surface, was compared with IgG adsorbed on various silica surfaces. This comparison showed that the covalently bound IgG has a superior stability when the pH was lowered or incubation with detergents, urea or ethylene glycol was carried out. The result was evaluated by ellipsometry, an optical technique that renders possible the quantification of amounts of immobilized IgG. The results outline the possibilities of obtaining a controlled covalent binding of biomolecules to solid surfaces with an optimal stability and biological activity of the immobilized molecules.

scholarly journals Immobilization of immunoglobulins on silica surfaces. Kinetics of immobilization and influence of ionic strength

1985 ◽  
Vol 227 (2) ◽  
pp. 373-378 ◽  
Author(s):  
U Jönsson ◽  
M Malmqvist ◽  
I Rönnberg
Keyword(s):  
Ionic Strength ◽  
Surface Chemistry ◽  
Solid Surface ◽  
Surface Concentration ◽  
Covalent Attachment ◽  
Exchange Reactions ◽  
Silica Surfaces ◽  
Measuring Devices ◽  
Different Types ◽  
Kinetics Of

The kinetics of, and the influence of ionic strength on, the immobilization of rabbit immunoglobulin G (IgG) on different types of well-characterized silica surfaces were investigated. Adsorptive immobilization was compared with covalent attachment via thiol-disulphide exchange reactions. The amount of immobilized IgG on five different types of silica surfaces as a function of IgG concentration, at two different ionic strengths, was determined. The IgG-solid-surface interaction involved different types of interaction forces, depending on the surface chemistry of the solid surface. The solid-surface chemistry is an important parameter determining the immobilized amount of IgG. When conditions for covalent attachment of IgG to the surfaces were fulfilled, the IgG showed high affinity and the immobilized amount of IgG showed a fast saturation. Changes in ionic strength showed no significant influence on the kinetics of immobilization on these surfaces. The amount of covalently attached IgG was partially ionic-strength-dependent, indicating that adsorptive interactions were involved. The results are of fundamental interest for the development of new immunosensors based on surface-concentration-measuring devices.

scholarly journals The role of double covalent flavin binding in chito-oligosaccharide oxidase from Fusarium graminearum

2008 ◽  
Vol 413 (1) ◽  
pp. 175-183 ◽  
Author(s):  
Dominic P. H. M. Heuts ◽  
Remko T. Winter ◽  
Gerke E. Damsma ◽  
Dick B. Janssen ◽  
Marco W. Fraaije
Keyword(s):  
Redox Potential ◽  
Fusarium Graminearum ◽  
Covalent Binding ◽  
Site Directed Mutagenesis ◽  
Wild Type ◽  
Covalent Bonds ◽  
Regioselective Oxidation ◽  
Flavin Binding ◽  
High Redox Potential

ChitO (chito-oligosaccharide oxidase) from Fusarium graminearum catalyses the regioselective oxidation of N-acetylated oligosaccharides. The enzyme harbours an FAD cofactor that is covalently attached to His94 and Cys154. The functional role of this unusual bi-covalent flavin–protein linkage was studied by site-directed mutagenesis. The double mutant (H94A/C154A) was not expressed, which suggests that a covalent flavin–protein bond is needed for protein stability. The single mutants H94A and C154A were expressed as FAD-containing enzymes in which one of the covalent FAD–protein bonds was disrupted relative to the wild-type enzyme. Both mutants were poorly active, as the kcat decreased (8.3- and 3-fold respectively) and the Km increased drastically (34- and 75-fold respectively) when using GlcNac as the substrate. Pre-steady-state analysis revealed that the rate of reduction in the mutant enzymes is decreased by 3 orders of magnitude when compared with wild-type ChitO (kred=750 s−1) and thereby limits the turnover rate. Spectroelectrochemical titrations revealed that wild-type ChitO exhibits a relatively high redox potential (+131 mV) and the C154A mutant displays a lower potential (+70 mV), while the H94A mutant displays a relatively high potential of approximately +164 mV. The results show that a high redox potential is not the only prerequisite to ensure efficient catalysis and that removal of either of the covalent bonds may perturb the geometry of the Michaelis complex. Besides tuning the redox properties, the bi-covalent binding of the FAD cofactor in ChitO is essential for a catalytically competent conformation of the active site.

Silica Surface Modification Reactions with Aluminum and Boron Alkyls and (Alkyl)Chlorides: Reactivities and Surface Nanostructures

2008 ◽  
Vol 8 (2) ◽  
pp. 660-666 ◽  
Author(s):  
Jonathan P. Blitz ◽  
Jeannine M. Christensen ◽  
Carol A. Deakyne ◽  
Vladimir M. Gun'ko
Keyword(s):  
Chemical Structure ◽  
Silica Surface ◽  
Molecular Level ◽  
Ring Structure ◽  
Membered Ring ◽  
Silica Surfaces ◽  
Surface Nanostructures ◽  
Reactive Groups ◽  
Aluminum Compounds ◽  
Silica Surface Modification

The functionalization of nanoporous and nanoparticulate silica surfaces requires a molecular level understanding of the chemistry and structures which result from surface reactions. Various types of reactive groups on silica can participate, giving rise to different nanostructures. It is necessary to devise methods to alter the reactive nature of silica surfaces to control the nanoscale chemical structure. Various silica pretreatments are utilized to alter the silica surface prior to reaction with AlEt3, AlEtxCl3−x, BEt3, BCl3, and TiCl4. Reactivities of these surface reactive reagents are compared. Aluminum compounds preferentially react with loss of alkane rather than HCl, in a thermodynamically controlled reaction as determined by ab initio computational methods. Consideration of the structures resulting from reaction of the boron and aluminum compounds above with silica surface diols has been taken into account. Particular attention has been paid to the possibility of forming a cyclic 4-membered ring structure. While this is unlikely to form from reactions with MCl3, such structures may be possible when reacting silicas with MMe3.

Mobility of pyrene on chemically modified silica surfaces

1988 ◽  
Vol 60 (22) ◽  
pp. 2487-2493 ◽  
Author(s):  
Jan. Staahlberg ◽  
Mats. Almgren ◽  
Jan. Alsins
Keyword(s):  
Modified Silica ◽  
Silica Surfaces ◽  
Chemically Modified ◽  
Chemically Modified Silica

scholarly journals SYNTHESIS AND PROPERTIES OF MODEL SYSTEMS, WITH THEIR USE IN STUDYING THE SCHIFF REACTION IN HISTOCHEMISTRY

1964 ◽  
Vol 12 (7) ◽  
pp. 533-537 ◽  
Author(s):  
M. J. HARDONK ◽  
P. VAN DUIJN
Keyword(s):  
Sulfhydryl Groups ◽  
Phosphate Group ◽  
Model Systems ◽  
Cellulose Derivatives ◽  
Amino Groups ◽  
Cellulose Films ◽  
Reactive Groups ◽  
Schiff Reaction ◽  
Cellulose Membranes ◽  
Covalently Bound

The synthesis of cellulose films containing several reactive groups is described. These films were developed for use as histochemical model systems to study several Schiff-type reactions. The synthesized model systems include cellulose membranes to which amino groups are covalently bound, cellulose membranes containing sulfhydryl groups, and cellulose membranes to which deoxyribonucleotides have been bound by means of their phosphate group. Evidence is given for the structure of these cellulose derivatives.

scholarly journals Kinetics of Enzyme Attack on Substrates Covalently Attached to Solid Surfaces: Influence of Spacer Chain Length, Immobilized Substrate Surface Concentration and Surface Charge

Langmuir ◽  
2008 ◽  
Vol 24 (20) ◽  
pp. 11762-11769 ◽  
Author(s):  
Joseph Deere ◽  
Rui F. De Oliveira ◽  
Bartłomiej Tomaszewski ◽  
Sarah Millar ◽  
Antonia Lalaouni ◽  
...  
Keyword(s):  
Surface Charge ◽  
Chain Length ◽  
Substrate Surface ◽  
Surface Concentration ◽  
Solid Surfaces ◽  
Spacer Chain Length ◽  
Immobilized Substrate ◽  
Kinetics Of
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