Multipoint attachment

Apart from enabling rapid prediction of solute retention, the Soczewinski equation allows a moleeular-level scrutiny of the solute — stationary phase interactions. The numeiieal value of the parameter n from Equation 2.14, which is at least approximately equal to unity (n 1), gives evidence of the one-point attachment of the solute moleeule to the stationary phase surface. The numeiieal values of n higher than unity prove that in a given chromatographic system, solute molecules interact with the stationary phase in more than one point (the so-ealled multipoint attachment). 

Multipoint attachment theory, 24 247 Multi-point fuel injection system, 10 51 Multiproduct batch processes, 20 723 Multipurpose batch pilot plants, 19 459 Multipurpose canister (MPC), radioactive waste transport in, 25 855 Multipurpose/multiproduct batch plants, 26 1000... 

HPMA copolymers are water-soluble biocompatible polymers, widely used in anticancer drug delivery (reviewed in Reference [22]). HPMA copolymers containing reactive groups at side-chain termini were previously used for the modification of trypsin [23], chymotrypsin [23,24], and acetylcholinesterase [25]. The modification dramatically increased the acetylcholinesterase survival in the blood stream of mice and the thermostability of modified enzymes when compared to the native proteins. However, the modification involved multipoint attachment of the copolymers to the substrates, which may cause crosslinking. To modify proteins or biomedical surfaces by one point attachment, semitelechelic polymers should be used. 

Multipoint attachment to a support protects the enzyme from inactivation by organic solvents. Mozhaev et al. (1990) have recently demonstrated that covalent linkage to polyacrylamide gel stabilizes df-chymotrypsin from denatmation by alcohols, the stabilizing effect increasing with the number of bonds between the protein and the support. 

Mozhaev, V.V., Sergeeva, M.V. Belora, A.B. and Khmelnitsky, Y.L. (1990) Multipoint attachment to a support protects enzyme from inactivation by organic solvents -chymotrypsin in aqueous solutiuons of alcohols and diols. Biotechnol. Bioeng., 35, 653-659. 

Clearly, proteins with a high concentration of binding sites on their surfaces may adsorb in the proper orientation, resulting in a multipoint attachment and high adsorption-free energy, even without any conformational adjustment. Thus, hysteresis can be present in some systems even at very short contact times. Proteins with very stable tertiary or quaternary structures may not show significant time-dependence due to the low probability for conformational change. 

Thermoresponsive acrylamide co-polymers were also used to alter the physicochemical and biopharmaceutical properties of avidin. Similar to PEG, the acrylamide co-polymers with a lower critical solution temperature (LCST) of about 37 °C were conjugated to the protein amino groups. The polymers were conjugated either by polymer multipoint attachment using polyfunctional polymers or by single chain attachment using end-chain monoactivated polymer. In both cases, the polymer conjugation was found to produce bioactive derivatives with reversible thermal character (Fig. 11.12). 

How does immobilization stabilize a protein First, it reduces the inter-molecular interaction, thus abolishing aggregation (38). Second, it minimizes the unfolding of the protein molecule by multipoint attachment to the matrix. Thus, the number of attachment bonds between the enzyme and the matrix correlates well with the enhancement in stability achieved as a result of immobilization (39). Mozhaev et al. (39) note that this stabilization cannot be pushed beyond a certain limit because irreversible denaturation is always possible. 

The use of lectins and glycosylated enzymes in bioanalytical systems is depicted schematically in Fig. 1. These systems are especially useful when assays require labile and expensive enzymes, because small amounts of enzymes can be added and they need to remain active for only short time periods. Most enzyme-based assays are based on the use of stable enzymes and that has restricted the development of new assays. In principle, this concept would also be useful for cells, but because of multipoint attachment it may be cumbersome to regenerate the sorbent. 

Multipoint attachment of proteins to gold electrode surfaces modified with an alkylthiol SAM... 

Inactivation under more stringent production conditions (37°C) revealed a significantly more stable biocatalyst when immobilization was performed on a high density oxirane carrier, although some influence of the different carrier backbone could not be completely ruled out (see Fig. 4). One possible explanation is an improved conformational stabilization by a higher degree of multipoint attachment. 

Its strong adsorption to the particle or droplet by multipoint attachment with several alkyl chains this ensures a lack of desorption and displacement of the... 

When >0.5, becomes negative (attractive) this, combined with the van der Waals attraction at this separation distance, produces a deep minimum causing flocculation. In most cases, there is a correlation between the critical flocculation point and the 0-condition of the medium. A good correlation is found in many cases between the critical flocculation temperature (CFT) and the 0-temperature of the polymer in solution (with both block and graft copolymers the 0-temperature of the stabilising chains A should be considered) [2]. A good correlation was also found between the critical volume fraction (CFV) of a nonsolvent for the polymer chains and their 0-point under these conditions. In some cases, however, such correlation may break down, and this is particularly the case for polymers that adsorb by multipoint attachment. This situation has been described by Napper [2], who referred to it as enhanced steric stabilisation. 

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