Crosslinking intermolecular

Elzinga, M. Phelan, J.J. (1984). F-actin is intermolecularly crosslinked by NN phenylenedimaleimide through lysine 191 and cysteine 374. Proc. Natl. Acad. Sci. USA 81, 6599-6603. 

C. BSC-PEG (1 g, 0.4 mequiv. SC-groups) was added to a stirred solution of BSA (100 mg, 1.5 x 10 6 mol) in 0.1 M sodium borate, pH 9.2. Sodium hydroxide (0.5 N) was used to maintain pH 9.2 for 30 min. The excess of free PEG was removed by diafiltration and the product assayed for the number of free amino groups. Approximately 48 of the amino groups of the native BSA were modified. Analysis of the product by HPLC (Gel Filtration) indicated that over 65% of PEG-BSA was in an intermolecularly crosslinked form and about 35% of the product had the same molecular weight as PEG-BSA from the above example. 

For a crosslinking polyreaction the functionality of the monomers is the basic parameter. However, it was found long ago that, after their reaction, not all functional groups are involved in intermolecular crosslinks but also in intramolecular and cyclic links. 

Intermolecular crosslinking between pendant vinyl groups and radical centers located on different macromolecules produce crosslinks that are responsible for the aggregation of macromolecules, which leads to the formation of a macrogel. It must be remembered that both normal and multiple crosslinks may contribute to the rubber elasticity of a network, whereas small cycles are wasted links. 

Figure 6 Mechanism of intermolecular crosslink formation in lysine-containing polypeptides via condensation with bis(AA-hydroxysuccinimidyl)suberates (R = Hm DMSO reactions R = S03 Na in aqueous reactions). 

Alkylating agents are compounds capable of reacting covalently with DNA bases. If a compound of this type contains two reactive groups, intramolecular or intermolecular crosslinking of the DNA double helix and bending of the double strand occurs. Examples of this type shown here are cyclophosphamide and the inorganic complex cisplatin. Anthracyclines such as doxorubicin (adriamy-cin) insert themselves non-covalently between the bases and thus lead to local alterations in the DNA structure (see p. 254 B). 

In the foregoing consideration the effect of intramolecular cross-linking on network formation and the gel point was not taken into account. In reality intermolecular crosslinking is always accompanied by closed loop formation. Every new bond between segments of the same (branched) polymer chain is an intramolecular crosslink if it does not increase its molecular weight. In a network a crosslink is intermolecular... 

FI3. Fox, T. G., and J. C. H. Hwa Crosslinked polymers. III. Efficiency of intermolecular crosslinking before gelation in methyl methacrylate-diacrylate and dimethacrylate copolymers. Vortrag vor der Polymer Division of the 131st National Am. Chem. Soc. Meeting, Miami 1957. 

Molecular weights were very high, increased up to a critical number of EO groups (n=41) and then decreased. In runs with n=21 and 41, the macrogel is also formed. Gelation also took place which is attributed to intermolecular crosslinking. 

Formaldehyde introduces both intramolecular and intermolecular crosslinks between proteins involving hydroxymethylene bridges, which change the three-dimensional structure of proteins. Such changes involve the tertiary and quaternary structures of proteins, whereas the primary and secondary structures are little affected. It has been shown that the secondary structure of purified protein molecules remains mostly unaltered during fixation with formaldehyde (Mason and O Leary, 1991). Even when the quaternary structure is changed by formaldehyde fixation, the secondary structure can remain intact. 

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