Functionalization, post-synthetic

Zeolites are formed by crystallization at temperatures between 80 and 200 °C from aqueous alkaline solutions of silica and alumina gels in a process referred to as hydrothermal synthesis.15,19 A considerable amount is known about the mechanism of the crystallization process, however, no rational procedure, similar to organic synthetic procedures, to make a specifically designed zeolite topology is available. The products obtained are sensitive functions of the reaction conditions (composition of gel, reaction time, order of mixing, gel aging, etc.) and are kinetically controlled. Nevertheless, reproducible procedures have been devised to make bulk quantities of zeolites. Procedures for post-synthetic modifications have also been described.20 22... 

Strategies for functionalization have been developed that exploit the naturally occurring amino acids as well as the non-natural ones. Post-synthetic modifications have been reported that are based on reactive sites that self catalyze the incorporation of the new functionality at the side chains of Lys residues [24,25] and on the chemoselective ligation reaction [26-29]. These developments in combination with new methodology for the synthesis of large proteins [30] provide access to a highly versatile pool of new polypeptides and proteins. 

Post-synthetic functionalization reactions have been reported that make it possible to introduce new groups into folded proteins and peptides using natural [24, 25] as well as non-natural amino acids [26-30]. The disulfide exchange... 

The four core histones, H2A, H2B, H3, H4 and their variants, and the linker histone HI subtypes are susceptible to a wide range of post-synthetic modifications, including acetylation, phosphorylation, methylation, ubiquitination, and ADP-ribosylation (Figs. 1 and 2). In this chapter, the four latter modifications and their functions in chromatin structure and function are presented. 

There are two principal modes for introducing the photophore into a peptide (1) Coupling a photoreactive N-protected amino acid during the stepwise assembly of the peptide e.g. in Scheme 3, the amino acid 4-benzoylphenylalanine (3) is incorporated into position 8 of substance P (9). (2) Post-synthetic modification of a fully assembled peptide, at either a free N-terminal a-amino group or a side-chain functionality, by the photophore in a site-specific or nonspecific manner e.g. in Scheme 3, treatment of cyclic R-G-D-containing peptide 10 with 4-benzoylbenzoic anhydride (11) gives the modified peptide 12. 

The amino-terminal sequence information plays a critical role 1) when the entire primary structure is ready to be constructed from many sequences assigned for small peptide fragments 2) when protein processing is involved in which amino-terminal region of translated polypeptide receives site specific cleavage reaction to produce mature, functional protein 3) when post-synthetic modification is involved in which amino-terminal end group receives some sort of modification, such as acetylation. 

Histones are also subject to reversible post-synthetic modifications, including phosphorylation, acetylation, and poly ADP-ribosylation. The functions of these modifications remain to be fully established, but there are good indications that ... 

Fatty acids attached to membrane phospholipids can be post-synthetically converted to their cyclopropane derivatives during the stationary phase of bacterial growth. Their biosynthesis and function have been elucidated by the Cronan s laboratory (D.W. Grogan,... 

Figure 1. Evolution of the TPD spectra of the post-synthetically modified zeolites as a function of the cesium loading P CsNaX Q CsNaX 4 Cs CsNaX 9 Cs CsNaX 11 Cs M CsNaX 16 Cs-.Q CsNaX 26 Cs.

Post Synthetic Modification.— Various methods have been used to modify tRNA in order to relate its structure to its function in the reactions of protein synthesis. Excision of the Y nucleotide from yeast tRNA using the method reported last year, followed by resealing of the anticodon loop with T4 RNA ligase gives modified tRNA , with six nucleotides in the anticodon loop instead of seven, which is virtually non-chargeable with phenylalanine, although the half-molecules used to prepare the modified tRNA were chargeable. A... 

Post-synthetic modification methods (route A in Figure 36.2) rely on the presence of silanol groups on the inside of the pore walls. The simplest type of post-synthetic modification is the hydrophobization of the calcined mesoporous materials by reaction with alkylchloro- or alkylalkoxy-silanes, - " but functional groups and metal complexes can also be attached. - " ... 

The 3-bromopropyl-substituted nucleoside phosphoramidite 244 has been prepared, with a view to its incorporation into oligonucleotides which would permit post-synthetic functionalization of the sugar moiety on the solid support by reaction with appropriate nucleophiles. ... 

The 2 -0-(3-bromopropoxy)methyl group has been introduced at 0-2 of ribonucleosides, permitting post-synthetic functionalization of the sugar units of oligonucleotides on the solid support by nucleophilic substitution. ... 

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