2. The 20 amino acids are usually grouped according to the properties(mainly polarity) of their r groups 2.1 Six amino acids have nonpolar, aliphatic Hydrophobic)r groups. They are Gly, Ala, val, Leu, Ile, and met. gly has a hydrogen as its r group having minimal steric hindrance In protein structure Gly offers the most flexibility Ala, Val, Leu, lle and met have hydrocarbon r groups, often involved in hydrophobic interactions
2. The 20 amino acids are usually grouped according to the properties (mainly polarity) of their R groups 2.1 Six amino acids have nonpolar, aliphatic (hydrophobic) R groups. •They are Gly, Ala, Val, Leu, Ile, and Met. •Gly has a hydrogen as its R group, having minimal steric hindrance. •In protein structure Gly offers the most flexibility! •Ala, Val, Leu, Ile and Met have hydrocarbon R groups, often involved in hydrophobic interactions
GIy,G,甘氨酸 Nonpolar, aliphatic R groups Ala,A,丙氨酸 COO coo COO VaL,V,缬氨酸 H3 N--C-H H3N--C-H H3N--C-H Leu,L,亮氨酸 H CH CH Ie,I,异亮氨酸 CH. Ch Met,M,蛋氨酸, Glycine Alanine Valine 甲硫氨酸 COO COO COO H3N--C-H H3N-C-H H3N--C-H CH2 CH H-C—CH3 CH CH CHa CHs CH3 CHs CHs Leucine Methionine Isoleucine
Gly, G, 甘氨酸 Ala, A, 丙氨酸 Val, V, 缬氨酸 Leu, L, 亮氨酸 Ile, I, 异亮氨酸 Met, M, 蛋氨酸, 甲硫氨酸
2.2 Ser, Thr, Asn, GIn, Cys, and Pro have polar uncharged r groups. The r groups are more hydrophilic, due to the presence of hydroxyl groups, sulfur atoms, or amide groups. SH group of two Cys in proteins can be oxidized to form a covalent disulfide bond Cys often participates in hydrophobic interactions. Pro has an imino group, instead of an amino group, forming a five-membered ring structure, being rigid in conformation .Pro is often found in the bends of folded protein chains and often present on the surface of proteins. It offers the least flexibility
2.2 Ser, Thr, Asn, Gln, Cys, and Pro have polar, uncharged R groups. •The R groups are more hydrophilic, due to the presence of hydroxyl groups, sulfur atoms, or amide groups. •-SH group of two Cys in proteins can be oxidized to form a covalent disulfide bond. •Cys often participates in hydrophobic interactions. •Pro has an imino group, instead of an amino group, forming a five-membered ring structure, being rigid in conformation. •Pro is often found in the bends of folded protein chains and often present on the surface of proteins. It offers the least flexibility
Ser,S,丝氨酸 Thr,T,苏氨酸 Polar, uncharged R groups Cy,C,半胱氨酸 COO COO COO HRN-C-H HN-C-HHN—C-H Pro,P,脯氨酸 CHoO H-C-OH CH2 Asn,N,天冬酰胺 CH3 SH GIn,Q,谷氨酰胺 Serine Threonine Cysteine COo cOo cOo HoN-C-H HSN-C-H H2n CH2 CH2 CH2 H2C—CH2 CH2 HON HoN Proline Asparagine Glutamine
Ser, S, 丝氨酸 Thr, T, 苏氨酸 Cys, C, 半胱氨酸 Pro, P, 脯氨酸 Asn, N, 天冬酰胺 Gln, Q, 谷氨酰胺
COO COO H3N一CH H3N--CH Cysteine CH2 CH2 2H+2e SH Cystine SH 2H++2e CH CH Cysteine CH--NHs CH一NH cOo cOo Cystine(胱氨酸) is dimer of cycteine(半胱氨酸)
Cystine (胱氨酸) is dimer of cycteine (半胱氨酸)