Tyrosine solution preparation

Protein concentration can also be determined by measuring the intrinsic fluorescence based on fluorescence emission by the aromatic amino acids tryptophan, tyrosine, and/or phenylalanine. Usually tryptophan fluorescence is measured. The fluorescence intensity of the protein sample solution is measured and the concentration is calculated from a calibration curve based on the fluorescence emission of standard solutions prepared from the purified protein. This assay can be used to quantitate protein solutions with concentrations of 5 to 50 (J-g/ml. 

D-Tyrosine solution (10 mg/ml) Prepare in water, store at -l-4°C, and use to quench the iodination reaction. 

After four or five days, with daily shakings, most of the casein is in solution and chalky masses of tyrosine begin to separate. After five days, a second dose of 20 g. of pancreatin in 100 cc. of water is added. After twelve days, the bottle is cooled in an ice-box over night and the undissolved material is filtered off (Note 4) and reserved for the preparation of tyrosine. 

Solution-phase enantioselective synthesis of 437 and 438 thus achieved was also translated into solid-phase synthesis <2002TL8981>. The oxazolidinone 441 prepared from L-tyrosine methyl ester via 440 was attached to Merrifield resin to produce 442. Resin-bound 442 was converted to 443 (Scheme 98). 

Difficulties encountered in the postsynthetic chemical sulfation of peptides and the correspondingly low yields have led to the proposal of an alternative approach. This approach makes use of appropriate tyrosine 0-sulfate derivatives for the chain elongation steps in solution and on solid supports by applying protection strategies compatible with the acid sensitivity of the sulfate ester. Moreover, the analytical characterization of the peptides synthesized with tyrosine 0-sulfate derivatives is greatly facilitated since contaminations deriving from the preparation of the intermediates are easily detected by chromatographic (HPLC and CE) and spectroscopic methods (see Table 2). 

Unlabeled amino acid solution (10 x stock) See Table 3.2.6. These amino acids, which are included in the natural L-amino acid kit (ICN Biomedical, 100586), except for the two alkaline amino acids (cystine and tyrosine), are mixed into a 100-ml volumetric flask. Then, 10 ml of L-glutamine (200 mM, Sigma G7513 must be in solution before use) and 50 ml water are added and the solution stirred until all components are dissolved. For L-cystine and L-tyrosine, the indicated amount is added to a 10-ml volumetric flask and the pH adjusted to > 8.0 by adding 2N NaOH drop by drop until the amino acids are dissolved. Then water is added to the 10-ml mark and the solution transferred to a 100-ml flask to complete the solution. Aliquots of 10 ml are prepared using 15-ml conical screw-top tubes and stored at -80°C. 

The preparation of a bis-O-ferrocenoyl-L-tyrosine peptide 106 has been reported (Scheme 31 ).t69i This compound was rationally designed to be used as a model peptide to study the binding ability of a fullerene-modified silica gel. The attachment of the ferrocenyl units was performed presumably in solution using the free hydroxy tyrosine peptide and ferrocenoyl chloride. 

Sodium phosphate buffer, 0.05 M, pH 7. 0 Mushroom tyrosinase, 100 umts/mL 1 unit represents the amount of enzyme that causes an A280 change of 0.001 using tyrosine as substrate. Prepare solution in phosphate buffer A280 should be about 0.20. Store in ice bath dunng laboratory period. 

Determination of protein concentration by measuri ng absorbance at 280 nm (A2g0) is based on the absorbance of UV light by the aromatic amino acids tryptophan and tyrosine, and by cystine, disulfide bonded cysteine residues, in protein solutions. The measured absorbance of a protein sample solution is used to calculate the concentration either from its published absorptivity at 280 nm (a280) or by comparison with a calibration curve prepared from measurements with standard protein solutions. This assay can be used to quantitate solutions with protein concentrations of 20 to 3000 pg/ml. 

The Mitsunobu procedure for the incorporation of carbohydrate moiety into combinatorial peptide libraries has been executed on solution phase, by using gluco-tyrosine as glycoamino acid model (prepared as shown in Figure 3.15) and improved on a solid support for model peptide GlyGly-Tyr (jS-tetra acetyl glucose)-GlyGly. 

The electrophilic character of astatine in aqueous acidic solution has been taken advantage of to prepare carrier-free astatotyrosine (10), an important compound for biomedical investigations53. An optimal yield of ca 90% was obtained if an aqueous solution of astatine together with tyrosine was dissolved in a mixture of perchloric and acetic acid and heated in sealed ampoules to 150-160 °C for about 30 minutes. Raising the temperature to... 

Standard Curve Transfer 100.0 mg of L-tyrosine, chromatographic-grade or equivalent (Aldrich Chemical Co.), previously dried to constant weight, to a 1000-mL volumetric flask. Dissolve in 60 mL of 0.1 N hydrochloric acid. When completely dissolved, dilute the solution to volume with water, and mix thoroughly. This solution contains 100 pig of tyrosine in 1.0 mL. Prepare three more dilutions from this stock solution to contain 75.0, 50.0, and 25.0 pig of tyrosine per mL. Determine the absorbance of the four solutions at 275 nm in a 1-cm cell on a suitable spectrophotometer versus 0.006 N hydrochloric acid. Prepare a plot of absorbance versus tyrosine concentration. 

The traditional method for preparing (m-butyl ethers involves reacting a large excess of isobutene with a solution of the alcohol in dichloromethane in the presence of concentrated sulfuric acid, p-toluenesulfonic acid or phosphoric acid and the method is effective for protecting the side chain hydroxyl functions of serine, threonine [Scheme 4.123], and tyrosine.223 224 A more convenient method involving use of Amberlyst H-15 resin in hexane as the acid catalyst deserves wider attention.217... 

A"-Fmoc-Tyr(S03Na)OH was prepared by reacting tyrosine with chlorosulfonic acid in TFA at —20°C for 5 minutes. Then A"-Fmoc group was added by reacting with Fmoc-Cl in a mixture of 10% sodium carbonate solution and dioxane. 

The quantitative conversion of hydrazides into azides can be assessed by spra5nng spots of the reaction mixture on paper taken at time intervals with the hydrazide test solution, which is a freshly prepared 1 1 mixture of 0.3 M FeCh in 0.1 M AcOH and 0.2 M potassium ferricyanide in 0.1 M AcOH. Hydrazides give an intensive blue color and brown colored spots on quantitative formation of the azides. Phenols, i.e. unprotected tyrosine, also yields blue colored spots.)... 

The monoazo derivative of tyrosine formed with XX was prepared in the following way. A solution of 237 mg (1.0 mmole) of XX in 30 ml of 0.01 N HCl was added dropwise to N-chloroacetyltyrosine (309 mg, 1.2 mmoles) in 25 ml of 0.2 M sodium phosphate buffer, pH 6.2, with continuous stirring at 0°C. Aqueous sodium hydroxide was added constantly to maintain the reaction mixture at pH 6.2. Three hr after the completion of the addition of N-chloroacetyl tyrosine, the stirring was discontinued and the reaction mixture was left at room temperature overnight. The reaction mixture formed a gel and then was acidified to pH 2 with 12 N HCl. The product precipitated out and could be recrystallized from methanol and then aqueous acetone. The crystals thus obtained melted at 214-215° with decomposition. 

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