Crosslinking reagents design

Hydrophobic crosslinking reagents each with two photochemically ac-tivatable groups have been synthesized by Mikkelson and Wallach (1976). Their reagents (Fig. 5.1) were designed to bind to the lipid bilayer of... 

This section is designed to provide a general overview of activation and coupling chemistry. Some of the reagents discussed in this chapter are not themselves crosslinking or modification compounds, but may be used to form active intermediates with another functional group. These active intermediates subsequently can be coupled to a second molecule that possesses the correct chemical constituents, which allows bond formation to occur. 

The differences within these families of reagents generally relate to the length of the spacer or bridging portion of the molecule. Occasionally, the bridging portion itself is designed to be cleavable by one of a number of methods (Chapter 8). The great majority of homobifunctional, sulfhydryl-reactive crosslinkers mentioned in the literature are not readily available from commercial sources and would have to be synthesized to make use of them. The ones listed in this section are obtainable from Thermo Fisher. 

Sulfo-SAMCA, sulfosuccinimidyl-7-azido-4-methylcoumarin-3-acetate, is a heterobifunctional reagent similar in design to SAED (Section 3.9, this chapter) (Thermo Fisher). One end of the crosslinker contains an amine-reactive sulfo-NHS ester, while the other end is an AMCA derivative (Chapter 9, Section 3) that contains a photosensitive phenyl azide group. Unlike... 

Alternatively, shorter, discrete crosslinkers containing PEG spacers of known chain length are now available (Thermo Fisher, Quanta BioDesign see Chapter 18). These reagents are designed to contain an exact number of PEG units, typically from between 2 repeating units... 

Hydrophilic short biotin-PEG tags also have found their way into the design of multifunctional crosslinkers to study protein structures by mass spec. Fujii et al. (2004) developed a homobifunctional NHS ester crosslinker that in addition has a PEG-biotin handle (Figure 18.1). The reagent actually is a trifunctional compound similar to the biotinylated PIR compound... 

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