Measurement of amino acids

DEH Palladino, RM House, KA Cohen. Measurement of amino acid compositions of glycoprotein systems by gas-phase hydrolysis and reversed-phase high-performance chromatography. J Chro-matogr 599 3-11, 1992. 

Currently, measurements of amino acid composition are usually carried out on an amino acid analyzer, a device that automates the previously described operations. As illus-... 

Measurement of amino acid levels in the vitreous humor of rats after chronic intraocular pressure elevation or optic nerve transection. Glaucoma 11, 396—405. 

If the history, physical findings, and laboratory results are suggestive but not conclusive of a particular mitochondrial disease (e.g., MELAS), then a second tier of tests is performed. These include blood and CSF lactate and pyruvate, as well as the lactate/pyruvate ratio timed or random measurement of amino acids in blood, urine, and CSF organic acids in urine and CSF and ketones and free and total carnitine in blood and urine. 

It is possible to test equation (16) by means of solubility measurements of amino-acids in the presence of salts if /So is the solubility in a medium of ionic strength zero and dielectric constant Do, i.e., that in the pure solvent, and S is the solubility in a neutral salt solution of ionic strength p and dielectric constant D, then since /So/S is equal to the activity coefficient (cf. p. 177) it follows from equation (16) that... 

McCarthy, M., Hedges, J. I., Benner, R., and Fogel, M. (2003). Compound-specific delta N-15 measurements of amino acids in dissolved or nic matter from the central Pacific Ocean. Qeochim. Cosmochim. Acta 67(18), A284—A284. 

Pearson, H., Gust, D., Armitage, I. M., Huber, H., Roberts, J. D., Stark, R. E., Void, R. R., and Void, R. L. (1975). Proc. Nat. Acad. Sci. U.S.A. 72, 1599. Nuclear Magnetic Resonance Spectroscopy Reinvestigation of Carbon-13 Spin-Lattice Relaxation Time Measurements of Amino Acids. 

A hypothetical reference protein derived from the pattern of human amino acid requirements was proposed as a standard for comparison. Shortcomings have been recognized and progress has been made in accurately evaluating human amino acid requirements. Equally critical for success is the ability to obtain precise measurements of amino acid content in the protein sources. Finally, to improve on accuracy of scoring procedures, chemically determined amino acid contents may have to be corrected for digestibility or biological availability. 

Dawson, L. A., et al.. Rapid high-throughput assay for the measurement of amino acids from micro-dialysates and brain tissue using monolithic CIS-bonded reversed-phase columns, J. Chromatogr., B Analyt. Technol. Biomed. Life ScL, 807, 235, 2004. 

C. Carducci, M. Birarelli, V. Leuzzi, G. Santaga, P. Serafini and I. Antonozzi, Automated method for the measurement of amino acids in urine by high-performance liquid chromatography, /. Chromatogr., A, 1996, 729, 173-180. 

Fig. 3. Schematic representation of double-isotope dansyl microassaV for measurement of amino acids in brain.

CNS (medulla, pons, spinal cord). The assay has been applied to the measurement of amino acids in segments of autopsied human spinal cord, patients dying with the clinical diagnosis of Friedreich s ataxia were found to have selectively decreased concentration of glutamate and glutamine in gray matter of lumbar spinal cord (Butterworth and Giguere, 1984). 

A measure of the effect of assuming one or other of the measures of amino acid composition can be gained if we consider the following daily ration ... 

L chain, based on measurements of amino acid composition, are b4 versus b5, 15 b4 versus b6, 28 b5 versus b6, 17 (65,66). These are average values since they are obtained with heterogeneous populations of L chains. However, it seems quite possible that differences not associated with allotype would be minimized in such heterogeneous populations. This is supported by the identity in average composition with respect to most amino acids. 

From the measurements of amino acid analysis, the weight percent of amino acid residues in insulin was found as follows ... 

Using arteriovenons catheters, one can also measure the amino acid balance across a hmb, and measurements of amino acid transport, muscle protein synthesis, and breakdown can be made by simultaneously using stable isotopes.Another method to measure protein synthesis is the fractional synthetic rate (FSR) method. This requires the infusion of an isotope and the measurement of the incremental increase in isotopic enrichment within a tissue or specific protein over time. We, and others, have used muscle biopsies to look at mixed-skeletal muscle FSR after exercise using this method. Myofibrillar and mitochondrial FSR can also be determined using stable isotopic tracer incorporation in combination with a gel separation of the component proteins. A recent development has been the measurement of collagen synthesis in both muscle and tendons using the FSR method. With this method it has been shown that acute resistance exercise results in a rapid... 

Amino acids are simple building-block subunits of proteins, and their side chains determine the higher-order structures and the chemical functions of proteins. The FUV spectral measurements of amino acids especially in gas and solution states are very challenging, because the vapor pressures of amino acids are quite low [66], and the photoabsorption of solvents including water is very intense [7, 14]. Just a few FUV absorption spectra of amino acids were reported in the thin solid films [67,68], the gas states [69,70], and the solution states [71,72]. Actually, the FUV spectra of amino acids in aqueous solutions can be easily obtained by using the ATR method. This section will introduce the FUV spectra of 20 naturally occurring amino acids in pure water, acidic, and basic aqueous solutions in the region from 145 to 300 nm [73]. 

This method, proposed by Satterlee represents a modification of the chemical score technique. Amino acid analysis is used to determine the essential amino acid profile and an in-vitro proteolytic enzyme step estimates the overall digestibility of the test protein. The in-vitro protein digestibility data, together with the essential amino acid profile, are then used to predict the PER (c-PER). The results obtained so far indicate a good correspondence between the calculated PERs and the actual PERs in the rat assay. The c-PER value is thus an estimate of nutritive value, with correction of the chemical score for digestibility, but it is not a measure of amino acid availability. 

Here it is possible to use either a pNHs or a PH2S transducer [239]. The PH2S electrode is sensitive to CChf which limits its application somewhat because CO2 is produced by the respiratory metalwlism of bacteria. Consequently, the pNHs electrode is usually chosen for coupling with microorganisms for the measurement of amino acids [240, 241],... 

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