Acetyl-histidine

Protection was determined as described in Table 11. S026-B is from T4 lysozyme, P is from BPTl, (iNCT-pl and Fos-pl are leucine zippers Ac, acetyl. Histidines were ignored in determining net charge. Adapted from Randall (1992). C opyright 1992 by the AAAS. 

Neurosine N-acetyl-histidine Central nervous system and eyes 1964... 

As standards for spectrophotometric measurements, Traylor and Singer (1967) prepared the monoazo derivatives of histidine and tyrosine with the various diazonium salts. The spectra of the products of reaction of N-acetyl histidine with the diazonium salt were obtained after reaction of a 100-fold excess of N-acetyl histidine with the diazonium salt in 0.1 M borate at pH 9.0. The spectral constants for the histidine and tyrosine derivatives are recorded in Table 5.1. 

Park JS, Han TH, Lee KY, Han SS, Hwang JJ, Moon DH, Kim SY, Cho YW. N-acetyl histidine-conjugated glycol chitosan self-assembled nanoparticles for intracytoplasmic delivery of drugs Endocytosis, exocytosis and drug release. J Control Release 2006 115 37-45. 

Figure 3. 360 MHz H FT nmr spectra (10 pulsesl of 2.5 x 10"2 M N-acetyl histidine and 2 x lO" m flavin I at pH = 7.5 taken with the pulse sequence of Figure 1, (a) light spectrum, (bl dark spectrum, (c) difference a-b. The lower trace is a part of spectrum c with the vertical scale reduced by a factor 8.

In N-acetyl-hlstidine such an Interaction between the positively charged a amino group and the lone pair at the N ir position Is not possible. The deprotonatlon of the Imidazole ring of that compound should result In shifts of Its N ir and N T resonances which are similar to those observed for histidine after deprotonatlon of the a amino group. Indeed we obtained values of the chemical shifts (-2oo.8 ppm and -169.o ppm) for the N ir zuid N t resonances of N-acetyl-histidine... 

Hence we have to consider a stacking association of a positively charged and a neutral imidazole ring of histidine. Ue obtain very similar results in the case of N-acetyl-histidine also which provides further evidence for this type of interaction. 

N-acetyl histidine-conjugated glycol chitosan self-assembled NPs For intracytoplasmic delivery of drugs [162]... 

The general procedure used in these studies is to trace-label samples of the protein with H-FDNB at several pH-values in the presence of N-acetyl-histidine or imidazole lactic acid as internal standard. The reaction mixture is then made chemically homogeneous by fully reacting with unlabelled or " C-FDNB. In the case of proteins containing more than one histidine residue, peptides are isolated so than an unequivocal assignment of parameters can be made. For proteins containing a solitary histidine residue, imidazolyl-DNP-histidine is isolated after acid hydrolysis. The internal standard is purified separately and the data from scintillation counting is substituted into Equations (1) or (2) to derive rate constants. 

Examples of micellar systems are given below where the surfactant provides the medium for catalysis but does not directly participate in the reaction. For instance, JV-acetyl histidine can bring about the hydrolysis of p-nitro-phenyl esters via an acyl-imidazole intermediate. 

N-Dodecyl-JV, N -dimethyl aminoethyl carbonate ion is hydrolyzed 2240 times faster with the following surfactant than with N-acetyl histidine. 

Bombesin peptide Bombesin was conjugated to JV-acetyl histidine-modified GC for targeting gastric-releasing peptide receptors overexpressed in prostate cancer cells. Iron oxide was loaded to be tested as a probe for MRI [34]... 

---