Tyrosine in peptides

Gorecki, M., Wilchek, M., and Patchornik, A. (1971) The conversion of 3-monoazotyrosine to 3-amino-tyrosine in peptides and proteins. Biochim. Biophys. Acta 220, 590-595. 

A more useful application of the electron-attracting effect of aryl subtituents is found in the cleavage of 4-picolyl derivatives of protected cysteine and tyrosine in peptide synthesis (Scheme 14).Catalytic cleavage of these derivatives is usually unattractive for SProtecting groups removable also include 3- and 4-picolyl esters. ... 

Previero, a., and E. Bordignon Controlled Modification of Tryptophan, Methionine, Cystine and Tyrosine in Peptides and Proteins. Gazz. Chim. Ital. 94, 630-638 (1964). 

The phenolic hydroxyl group of tyrosine, the imidazole moiety of histidine, and the amide groups of asparagine and glutamine are often not protected in peptide synthesis, since it is usually unnecessary. The protection of the hydroxyl group in serine and threonine (O-acetylation or O-benzylation) is not needed in the azide condensation procedure but may become important when other activation methods are used. 

An isopropyl ether was developed as a phenol protective group that would be more stable to Lewis acids than would be an aryl benzyl ether. The isopropyl group has been tested for use in the protection of the phenolic oxygen of tyrosine during peptide synthesis."... 

Me2P(0)Cl, Et3N, CHCI3, 76% yield. The Dmp group was used to protect tyrosine for use in peptide synthesis. It is stable to IM HCl/MeOH, 1 MHCl/AcOH, CF3CO2H, HBr/AcOH, and H2/Pd-C. 

The Src-homology 2 (SH2) domain is a protein domain of roughly 100 amino acids found in many signaling molecules. It binds to phosphorylated tyrosines, in particular peptide sequences on activated receptor tyrosine kinases or docking proteins. By recognizing specific phosphorylated tyrosines, these small domains serve as modules that enable the proteins that contain them to bind to activated receptor tyrosine kinases or other intracellular signaling proteins that have been transiently phosphorylated on tyrosines. 

Add from 5 pg to 500 pg of a tyrosine-containing peptide or protein dissolved in iodination buffer to the reaction mixture. 

Solubilities and stabilities of calcium phosphates in natural waters have been described (735), as have the nucleation and growth of calcium phosphate from solution (736). Several species have long been known to inhibit the precipitation of calcium phosphates, for example carbohydrates (646) and statherin, the tyrosine-rich peptide which occurs in saliva (737). The role of... 

K Rosenthal, A Karlstrom, A Unden. The 2,4-dimethylpent-3-yloxycarbonyl (Doc) group as a new nucleophile-resistant protecting group for tyrosine in solid phase peptide synthesis. Tetrahedron Lett 38, 1075, 1997. 

The enantiomeric purity of protected amino acids used in peptide synthesis can be determined by pre-column partial deprotection followed by derivatization with Marfey s reagent (116). The Marfey diastereoisomers can be easily resolved and determined by RP-HPLC using an ODS-Hypersil column288. Fifteen amino acids collected from mammalian tissues were derivatized with Marfey s reagent and subjected to two-dimensional TLC. Each individual spot (enantiomeric mixture of a diasteroisomer) was then resolved by RP-HPLC. Except for tyrosine (46) and histidine (117), subnanomole quantities of enantiomers could be analyzed289,290. 

There are several biologically important peptides which contain tyrosine but not tryptophan. These include small molecules with molecular weights of about 1000 or less. Molecules such as oxytocin, vasopressin, and tyrocidine A are cyclic, while others such as angiotensin II and enkephalin are linear. Schiller 19) has reviewed the literature up through 1984 on fluorescence of these and several other peptides. One major finding that has been reported recently is that the anisotropy and fluorescence intensity decays of many peptides are complex. This is especially evident in some of the tyrosine-containing peptides, and we expect that there will be considerable effort made over the next few years toward understanding the physical basis for these complex kinetics. 

The mobility of tyrosine in Leu3 enkephalin was examined by Lakowicz and Maliwal/17 ) who used oxygen quenching to measure lifetime-resolved steady-state anisotropies of a series of tyrosine-containing peptides. They measured a phase lifetime of 1.4 ns (30-MHz modulation frequency) without quenching, and they obtained apparent rotational correlation times of 0.18 ns and 0.33 ns, for Tyr1 and the peptide. Their data analysis assumed a simple model in which the decays of the anisotropy due to the overall motion of the peptide and the independent motion of the aromatic residue are single exponentials and these motions are independent of each other. 

X.-Y. Liu, K. O. Cottrell, and T. M. Nordlund, Spectroscopy and fluorescence quenching of tyrosine in lima bean trypsin/chymotrypsin inhibitor and model peptides, Photochem. 

The finding that the hydrolytic activity of the enzyme is retained after replacement of a tyrosine residue by phenylalanyl challenges the notion that a tyrosine acts as a general acid catalyst in peptide hydrolysis. It has been suggested that either the protonated Glu270 moiety or the zinc-water complex could perform the proton transfer [77]. 

Fluorescence is not widely used as a general detection technique for polypeptides because only tyrosine and tryptophan residues possess native fluorescence. However, fluorescence can be used to detect the presence of these residues in peptides and to obtain information on their location in proteins. Fluorescence detectors are occasionally used in combination with postcolumn reaction systems to increase detection sensitivity for polypeptides. Fluorescamine, o-phthalaldehyde, and napthalenedialdehyde all react with primary amine groups to produce highly fluorescent derivatives.33,34 These reagents can be delivered by a secondary HPLC pump and mixed with the column effluent using a low-volume tee. The derivatization reaction is carried out in a packed bed or open-tube reactor. 

The aromatic rings in the protein absorb ultraviolet light at an absorbance maximum of 280 nm, whereas the peptide bonds absorb at around 205 nm. The unique absorbance property of proteins could be used to estimate the level of proteins. These methods are fairly accurate with the ranges from 20 p,g to 3 mg for absorbance at 280 nm, as compared with 1 to 100 p,g for 205 nm. The assay is non-destructive as the protein in most cases is not consumed and can be recovered. Secondary, tertiary and quaternary structures all affect absorbance therefore, factors such as pH, ionic strength, etc can alter the absorbance spectrum. This assay depends on the presence of a mino acids which absorb UV light (mainly tryptophan, but to a lesser extent also tyrosine). Small peptides that do not contain such a mino acids cannot be measured easily by UV. 

The naturally occurring aromatic amino acids phenylalanine, tryptophane and tyrosine (Fig. 1) have been labelled with fluorine-18 through similar electrophilic substitution methods [7]. Aromatic residues contained in peptides have been labelled with CH3C02[ F]F [105,106], an example of direct labelling of macromolecules. However, direct labelling of macromolecules is usually not the method of choice nowadays (see Section 6). 

Aromatic amino acids are biogenetic precursors of neuroamines (dopamine, serotonin, histamine, etc.). On the other hand, phenylalanine (Phe) is frequently present in peptide sequences, while tyrosine is an important site of phosphorylation of proteins. Aromatic amino acids and neuroamines fluorinated on the aromatic ring have been the focus of many investigations. Indeed, after incorporation in polypeptides and proteins, they can be used as probes in NMR and in PET. 

Tyrosine (9-sulfate is stable under alkaline conditions, thus allowing for its quantification by amino acid analysis upon alkaline hydrolysis [0.2 M Ba(OH)2, 110 °C, 24 h] of sulfated tyrosine peptides and proteins.[6 331 Conversely, more than 95% of the ester is hydrolyzed after five minutes in 1M hydrogen chloride at 100 °C. Despite this pronounced acid lability, sulfated tyrosine peptides are sufficiently stable to short exposures of TFA134 35 or aqueous TFA[36 as required in peptide synthesis for removal of add-labile protecting groups. 

Conversely, exposure to hydrogen fluoride at 0 °C over short periods of time leads to almost quantitative hydrolysis.[37-39] In aprotic organic solvents, decomposition takes place unless the sulfate hemi-ester is neutralized with strong counterions.[37,381 The results of a detailed study are summarized in Figures 1 and 2t4°l which show the effect of various acids used in peptide chemistry in deprotection and in cleavage from the resin as well as the effect of temperature on the hydrolysis of tyrosine 0-sulfate as a sodium salt. 

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