Histone reagent

Since protamine is strongly basic, it forms salt-like complexes with various inorganic and organic acids. The sulfate, hydrochloride, nitrate, phosphate, and acetate salts are soluble in water, but the picrate, flavianate, and phosphotungstate salts are almost insoluble in water. Protamines also form scarcely soluble salts with silver nitrate, copper salts, mercury salts, etc. (Kossel, 1929). When heated to 60 °C with the Mirsky histone reagent (0.34 M mercuric sulfate in 1.88 M sulfuric acid) (Daly et al., 1951), protamine and histone are not precipitated whereas many other proteins precipitate. If the mixture is cooled to 0°C, the mercury salt of protamine is precipitated but histone remains in solution. This phenomenon can be utilized to distinguish protamine from histone. 

It has been found that DTBP cross-linking substantially increased the salt stability of the complexes. The salt stabilization is reversed upon the addition of DTT, which cleaves the bifunctional reagent, indicating that it is not due to the conversion of the amines to amidines and is dependent upon the cross-linking. Similar results were achieved with other polycations, including poly(allylamine), and histone HI. 

In the context of preparing potential inhibitors of histone deacetylase, Vasudevan and a team from Abbott have described the cyclization of 1,2-diacylhydrazides to 1,3,4-oxadiazoles with Burgess reagent under microwave conditions (150 °C, 15 min) (Scheme 6.224 a) [232], A different approach was chosen by Natero and coworkers, who prepared 2-chloromethyl-l,3,4-oxadiazoles by treatment of acyl hydrazides with 1-chloro-2,2,2-trimethoxyethane (Scheme 6.224b) [401]. Here, the reagent was used as solvent and the mixture was heated by microwave irradiation at 160 °C for 5 min. 

One of the very early research tools that were used to study the nucleosomal state of active genes were the nucleases, DNase I and Micrococcal nuclease. With the development of protocols for the isolation of nuclei from cells, it was possible to add these reagents to probe the accessibility of DNA. DNase I makes single nicks in double stranded DNA and when the DNA is associated with histones within the nucleosome, the DNA is extensively protected. Those nicks that are observed are found to occur only after extensive digestion and are limited to the outside surface of the DNA in 10 base increments [7,8]. Weintraub and Groudine in 1976 [9] first used this nuclease and observed that when nuclei from chicken erythrocytes were treated with DNase I, the active /1-globin gene was preferentially... 

Taunton J, Collins JL, Schreiber SL. (1996) Synthesis of natural and modified trapoxins, useful reagents for exploring histone deacetylase function. JAm Chem Soc 118 10412-10422. 

He, S. et al. (2003) Facile synthesis of site-specifically acetylated and methylated histone proteins reagents for evaluation of ihe histone code hypothesis. Proceedings of the National Academy of Sciences of the United States of America, 100, 12033-12038. 

Liu HL, Chen Y, Cui GH, Zhou JF. 2005. Curcumin, a potent anti-tumor reagent, is a novel histone deacetylase inhibitor regulating B-NHL cell line Raji proliferation. Acta Pharmacol Sin 26 603-609. 

Brown s crotylboration protocol was used effectively in the synthesis of azu-mamide A 28. Azumamides are unusual cyclic peptides that show potent inhibitory activity on histone deacetylase enzymes. A highly diastereo- and enan-tioselective (dr >99% 98% ee) crotylation of 3-benzyloxypropanal with the chiral reagent ( >crotyl-1Ipc2borane (l19E) afforded the homoallylic alcohol 29. Subsequent reductive ozonolysis and K2CO3-mediated hydrolysis of the acetate furnished the diol 3016 (Scheme 3.1m). 

Heimgartner s reagent, 2,4-bis-(p-tolylthio)-l,3,2A,, 4A, -dithiadiphosphetane-2,4-dithione HEPES, A-2-hydroxyethyl-piperazine-jV -2-ethane-snlfonie aeid HIMDA, A-hydroxyethyhminodiacetic acid Histones... 

Taunton, J., Collins, J. L., Schreiber, S. L. Synthesis of Natural and Modified Trapoxins, Useful Reagents for Exploring Histone Deacetylase Function. J. Am. Chem. Soc. 1996,118,10412-10422. 

Polymer-supported sulfonyl chlorides can be used for the selective monosulfonyl-ation of anilines, as demonstrated by the Ley group [71, 72], Commercially available polystyrene-DMAP (4-dimethylaminopyridine) was treated with different aryl sulfonyl chlorides to form polymer-bound sulfonylation reagents. These were reacted with substituted anilines to form an array of hydroxamic acids (Scheme 6.17), using a synthetic strategy involving polymer-bound reagents in all steps. The products were subsequently evaluated as histone deacetylase inhibitors. 

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