• Analytical Science and Technology
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• v.8 no.4
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• pp.575-582
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• 1995

A new analytical procedure using a serial dual electrode detector was developed for the analysis of amino acids and proteins. Bromine was generated at the upstream electrode and detected by the downstream electrode. The presence of amino acids and proteins was shown to lower the downstream current but with no apparent effect on the upstream current. This indirect mode of detection can be applied to the determination of amino acids and proteins which are electrochemically inactive or too large to be accessible to the electrode surface for electron exchange. The method is shown capable to determine various amino acids (cystine, tyrosine, lysine, tryptophan, glycine, methionine and arginine) and proteins (cytochrome c, hemoglobin, HAS, a-Amylase, Conalbumin I, Catalase and Myglobin) with linear working range for amino acids between $10^{-6}$ to $10^{-3}M$ and total proteins between $10^{-7}$ to $10^{-3}M$. The method has been applied for the analysis of amino acids and total protein in food using Flow Injection Analysis with results obtained comparable to those using the traditional analytical procedure. Use of pulse generation technique was shown to produce a more stable flow injection analysis peaks for repetitive determination than the use of conventional constant current method which showed increase of the background current after determination over 200 minutes. The pulse method was found to give stable baseline even after 400 minutes. Thus, the method is shown able to provide a suitable analytical procedure for automatic analysis of amino acids and proteins in food by flow injection analysis.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.4
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• pp.407-412
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• 1995

Experiments were conducted to obtain information on separation of nonviable seeds from seed lots by the nondestructive ways. Seeds of sesame, welsh onion and lettuce were artificially aged at 90% relative humidity and 45$^{\circ}C$ to get different seed qualities. The relationships between seed quality and leakage of total sugars, amino acids, and proteins into soaking water were determined to know a possibility of grading seeds. Dead seeds of lettuce leaked significant amounts of total sugars, amino acids, and proteins, while high quality seeds leaked negligeable amounts of total sugars and some of amino acids and proteins. Dead seeds of welsh onion leaked significant amounts of amino acids and some total sugars and proteins, while high quality seeds leaked negligeable amounts of these compounds. Sesame seeds leaked little total sugars, amino acids, and proteins regardless of seed quality.

• KSBB Journal
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• v.23 no.5
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• pp.355-361
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• 2008

Proteins carrying unnatural amino acids with novel side chains add a new dimension to studies of protein structure and function. This article provides an overview of the various strategies that have been developed to date for the synthesis of such proteins.

• Journal of The Korean Society of Grassland and Forage Science
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• v.32 no.4
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• pp.343-352
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• 2012

Sulphur deficiency has become widespread over the past several decades in most of the agricultural area. Oilseed rape (Brassica napus L.) is a very sensitive to S limitation which is becoming reduction of quality and productivity of forage. Few studies have assessed the sulphur mobilization in the source-sink relationship, very little is known about the regulatory mechanism in interaction between sulphur and nitrogen during the short-term sulphur deficiency. In this study, therefore, amount of sulphur and nitrogen incorporated into amino acids and proteins as affected by different S-supplied level (Control: 1 mM ${SO_4}^{2-}$, S-deficiency: 0.1 mM ${SO_4}^{2-}$, and S-deprivation: 0 mM ${SO_4}^{2-}$) were examined. The amount of sulphur in sulphate (S-sulphate) was significantly decreased by 25.8% in S-deprivation condition, compare to control, but not nitrogen in nitrate (N-nitrate). The markedly increase of sulphur and nitrogen incorporated amino acids (S-amino acids and N-amino acids) was observed in both S-deficiency and S-deprivation treatments. The amount of nitrogen incorporated proteins (N-protein) was strongly decreased as sulphur availability while the amount of sulphur incorporated into proteins (S-protein) was not affected. A highly significant ($p{\leq}0.001$) relationship between S-sulphate and S-amino acid was observed whereas the increase of N-amino acids is closely associated with decrease of N-proteins. These data indicate that increase of sulphur and nitrogen incorporated into amino acids was from different nitrogen and sulphur metabolites, respectively

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.103-113
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• 2014

Hydrophobicity is the key concept to understand the role of water in protein folding, protein self-assembly, and protein-ligand interaction. Conventionally, hydrophobicity of amino acids in a protein has been argued based on hydrophobicity scales determined for individual free amino acids, assuming that those scales are unaltered when amino acids are embedded in a protein. Here, we investigate how the hydrophobicity of constituent amino acids depends on the protein context, in particular, on the total charge and secondary structures of a protein. To this end, we compute and analyze the hydration free energy - free energy change upon hydration quantifying the hydrophobicity - of three short proteins based on the integral-equation theory of liquids. We find that the hydration free energy of charged amino acids is significantly affected by the protein total charge and exhibits contrasting behavior depending on the protein net charge being positive or negative. We also observe that amino acids in the central ${\beta}$-strand sandwiched by ${\beta}$-sheets display more enhanced hydrophobicity than free amino acids, whereas those in the ${\alpha}$-helix do not clearly show such a tendency. Our results provide novel insights into the hydrophobicity of amino acids, and will be valuable for rationalizing and predicting the strength of water-mediated interaction involved in the biological activity of proteins.

• YAKHAK HOEJI
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• v.39 no.4
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• pp.380-384
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• 1995

The isoelelectric points of Cd-BP(l) and Cd-BP(II), cadmium-binding proteins, were 6.01 and 5.35, respectively. Both of them contained zinc. As for the amino acid composition, Cd-BP(I) contained a lot of glycine and lysine but none of such aromatic amino acids as tyrosine and phenylalanine.. On the other hand, Cd-BP(II) contained leucine, histidine, asparti cacid and alanine but no aromatic amino acids.

• Journal of the Korean Data and Information Science Society
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• v.16 no.4
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• pp.745-758
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• 2005

This paper presents a statistical analysis on the position-specific distributions of amino acid residues in transmembrane proteins. A hidden Markov model segments membrane proteins to produce segmented regions of homogeneous statistical property from variable-length amino acids sequences. These segmented residues are analyzed by using chi-square statistic and relative-entropy in order to find position-specific amino acids. This analysis showed that isoleucine and valine concentrated on the center of membrane-spanning regions, tryptophan, tyrosine and positive residues were found frequently near both ends of membrane.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.163-166
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• 2016

Hydrophobicity is the key concept to understand the water plays in protein folding, protein aggregation, and protein-protein interaction. Traditionally, the hydrophobicity of protein is defined based on the scales of the hydrophobicity of residue, assuming that the hydrophobicity of free amino acids is maintained. Here, we explore how the hydrophobicity of constituting amino acids in protein rely on the protein context, in particular, on the total charge and secondary structures of a protein. To this end, we calculate and investigate the hydration free energy of three short proteins based on the integral-equation theory of liquids. We find that the hydration free energy of charged amino acids is significantly affected by the protein total charge and exhibits contrasting behavior depending on the protein total charge being positive or negative. We also observe that amino acids in the ${\beta}-sheets$ display more enhanced the hydrophobicity than amino acids in the loop, whereas those in the ${\alpha}-helix$ do not clearly show such a tendency. And the salt-bridge forming amino acids also exhibit increase of the hydrophobicity than that with no salt bridge. Our results provide novel insights into the hydrophobicity of amino acids, and will be valuable for rationalizing and predicting the strength of water-mediated interaction involved in the biological activity of proteins.

• Interdisciplinary Bio Central
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• v.1 no.2
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• pp.8.1-8.6
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• 2009

Introduction: It is a challenge to design a protein score function which stabilizes the native structures of many proteins simultaneously. The coarse-grained description of proteins to construct the pairwise-contact score function usually ignores the backbone directionality of protein structures. We propose a new two-body score function which stabilizes all native states of 1,006 proteins simultaneously. This two-body score function differs from the usual pairwise-contact functions in that it considers two adjacent amino acids at two ends of each peptide bond with the backbone directionality from the N-terminal to the C-terminal. The score is a corresponding propensity for a directional alignment of two adjacent amino acids with their local environments. Results and Discussion: We show that the construction of a directional adjacency-score function was achieved using 1,006 training proteins with the sequence homology less than 30%, which include all representatives of different protein classes. After parameterizing the local environments of amino acids into 9 categories depending on three secondary structures and three kinds of hydrophobicity of amino acids, the 32,400 adjacency-scores of amino acids could be determined by the perceptron learning and the protein threading. These could stabilize simultaneously all native folds of 1,006 training proteins. When these parameters are tested on the new distinct 382 proteins with the sequence homology less than 90%, 371 (97.1%) proteins could recognize their native folds. We also showed using these parameters that the retro sequence of the SH3 domain, the B domain of Staphylococcal protein A, and the B1 domain of Streptococcal protein G could not be stabilized to fold, which agrees with the experimental evidence.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.11
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• pp.1555-1559
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• 2001

In the first study of a series of experiment samples were taken from 11-13th rib of Hungarian Simmental (HS, n=22) and Holstein-Friesian (HF, n=18) cull cows. In the second one, that of females (n=15) and males (n=12) of HF breed was analysed for amino acid composition, and biological value (BV) of proteins. No significant influence of either breed or slaughter weight was established in this study. Thus, the essential amino acid content and biological value of the proteins in Hungarian Simmental breed are practically the same as in the Holstein-Friesian. On the other hand, gender proved to be a significant factor influencing the amino acid profile of beef proteins, as the quantity of essential amino acids turned out to be significantly larger in females than in males. No statistical difference could be established for the non-essential amino acids and BV between the two genders.