[Skip to Content](https://www.sigmaaldrich.com#main-content) [![MilliporeSigma](https://www.sigmaaldrich.com/static/logos/purple/millipore_sigma.svg)](https://www.sigmaaldrich.com/US/en) Products Cart0 USEN Products [Login / Register](https://www.sigmaaldrich.com/oidc-sign-in) [Order Lookup](https://www.sigmaaldrich.com/US/en/order-lookup) [Quick Order](https://www.sigmaaldrich.com/US/en/quick-order) Cart0 [Home](https://www.sigmaaldrich.com/US/en)[Protein Structural Analysis](https://www.sigmaaldrich.com/US/en/applications/protein-biology/protein-structural-analysis)Amino Acids Reference Chart # Amino Acids Reference Chart __Section Overview__ - [](https://www.sigmaaldrich.com#type)[Types of Amino Acids](https://www.sigmaaldrich.com#type) - [Properties of Common Amino Acids](https://www.sigmaaldrich.com#properties) - [Amino Acids by Side Chain](https://www.sigmaaldrich.com#side) - [Hydrophobicity Index for Common Amino Acids](https://www.sigmaaldrich.com#hydrophobicity) ## [](https://www.sigmaaldrich.com)Types of Amino Acids | | | | | |------------------------|---------------------------------------------------------------------|-----------------------------------------------------------------|-----------------------------------------------------------------| | Amino Acid | Reagent | Cell Culture & Molecular Biology | Analytical & Sensitive Applications | | Alanine (Ala/A) | [A7627](https://www.sigmaaldrich.com/US/en/product/sigma/a7627) | [A7469](https://www.sigmaaldrich.com/US/en/product/sigma/a7469) | [05129](https://www.sigmaaldrich.com/US/en/product/sigma/05129) | | Arginine (Arg/R) | [A5006](https://www.sigmaaldrich.com/US/en/product/sial/a5006) | [A8094](https://www.sigmaaldrich.com/US/en/product/sigma/a8094) | [11009](https://www.sigmaaldrich.com/US/en/product/sigma/11009) | | Asparagine (Asn/N) | [A8381](https://www.sigmaaldrich.com/US/en/product/sigma/a8381) | [A4284](https://www.sigmaaldrich.com/US/en/product/sigma/a4284) | [A7094](https://www.sigmaaldrich.com/US/en/product/sigma/a7094) | | Aspartic acid (Asp/D) | [A9256](https://www.sigmaaldrich.com/US/en/product/sigma/a9256) | [A7219](https://www.sigmaaldrich.com/US/en/product/sigma/a7219) | [A8949](https://www.sigmaaldrich.com/US/en/product/sigma/a8949) | | Cysteine (Cys/C) | [C7880](https://www.sigmaaldrich.com/US/en/product/sial/c7880) | [C6852](https://www.sigmaaldrich.com/US/en/product/sial/c6852) | [30129](https://www.sigmaaldrich.com/US/en/product/sigma/30129) | | | | [C7352](https://www.sigmaaldrich.com/US/en/product/sigma/c7352) | | | Glutamic acid (Glu/E) | [G1251](https://www.sigmaaldrich.com/US/en/product/sigma/g1251) | [G8415](https://www.sigmaaldrich.com/US/en/product/sigma/g8415) | [49449](https://www.sigmaaldrich.com/US/en/product/sigma/49449) | | Glutamine (Gln/Q) | [G3126](https://www.sigmaaldrich.com/US/en/product/sigma/g3126) | [G8540](https://www.sigmaaldrich.com/US/en/product/sigma/g8540) | [49419](https://www.sigmaaldrich.com/US/en/product/sigma/49419) | | | | [G7513](https://www.sigmaaldrich.com/US/en/product/sigma/g7513) | | | Glycine (Gly/G) | [G7126](https://www.sigmaaldrich.com/US/en/product/sigma/g7126) | [G8898](https://www.sigmaaldrich.com/US/en/product/sigma/g8898) | [50046](https://www.sigmaaldrich.com/US/en/product/sigma/50046) | | Histidine (His/H) | [H8000](https://www.sigmaaldrich.com/US/en/product/sial/h8000) | [H6034](https://www.sigmaaldrich.com/US/en/product/sigma/h6034) | [53319](https://www.sigmaaldrich.com/US/en/product/sigma/53319) | | Hydroxyproline (Hyp/O) | [H54409](https://www.sigmaaldrich.com/US/en/product/aldrich/h54409) | [H5534](https://www.sigmaaldrich.com/US/en/product/sigma/h5534) | | | Isoleucine (Ile/I) | [I2752](https://www.sigmaaldrich.com/US/en/product/sial/i2752) | [I7403](https://www.sigmaaldrich.com/US/en/product/sigma/i7403) | [58879](https://www.sigmaaldrich.com/US/en/product/sigma/58879) | | Leucine (Leu/L) | [L8000](https://www.sigmaaldrich.com/US/en/product/sigma/l8000) | [L8912](https://www.sigmaaldrich.com/US/en/product/sigma/l8912) | [61819](https://www.sigmaaldrich.com/US/en/product/sigma/61819) | | Lysine (Lys/K) | [L5626](https://www.sigmaaldrich.com/US/en/product/sial/l5626) | [L8662](https://www.sigmaaldrich.com/US/en/product/sigma/l8662) | [62929](https://www.sigmaaldrich.com/US/en/product/sial/62929) | | Methionine (Met/M) | [M9625](https://www.sigmaaldrich.com/US/en/product/sial/m9625) | [M5308](https://www.sigmaaldrich.com/US/en/product/sigma/m5308) | [64319](https://www.sigmaaldrich.com/US/en/product/sigma/64319) | | Phenylalanine (Phe/F) | [P2126](https://www.sigmaaldrich.com/US/en/product/sial/p2126) | [P5482](https://www.sigmaaldrich.com/US/en/product/sigma/p5482) | | | Proline (Pro/P) | [P0380](https://www.sigmaaldrich.com/US/en/product/sial/p0380) | [P5607](https://www.sigmaaldrich.com/US/en/product/sigma/p5607) | [81709](https://www.sigmaaldrich.com/US/en/product/sigma/81709) | | Serine (Ser/S) | [S4500](https://www.sigmaaldrich.com/US/en/product/sigma/s4500) | [S4311](https://www.sigmaaldrich.com/US/en/product/sigma/s4311) | [84959](https://www.sigmaaldrich.com/US/en/product/sigma/84959) | | Threonine (Thr/T) | [T8625](https://www.sigmaaldrich.com/US/en/product/sial/t8625) | [T8441](https://www.sigmaaldrich.com/US/en/product/sigma/t8441) | [89179](https://www.sigmaaldrich.com/US/en/product/sigma/89179) | | Tryptophan (Trp/W) | [T0254](https://www.sigmaaldrich.com/US/en/product/sial/t0254) | [T8941](https://www.sigmaaldrich.com/US/en/product/sigma/t8941) | [93659](https://www.sigmaaldrich.com/US/en/product/sigma/93659) | | Tyrosine (Tyr/Y) | | [T8566](https://www.sigmaaldrich.com/US/en/product/sigma/t8566) | [93829](https://www.sigmaaldrich.com/US/en/product/sigma/93829) | | | | [T1145](https://www.sigmaaldrich.com/US/en/product/sigma/t1145) | | | Valine (Val/V) | [V0500](https://www.sigmaaldrich.com/US/en/product/sial/v0500) | [V0513](https://www.sigmaaldrich.com/US/en/product/sigma/v0513) | [94619](https://www.sigmaaldrich.com/US/en/product/sigma/94619) | ## [](https://www.sigmaaldrich.com)Properties of Common Amino Acids NameMolecular WeightMolecular FormulaResidue FormulaResidue Weight (-H2O)pKa1pKb2pKx3pl4 [Alanine](https://www.sigmaaldrich.com/US/en/product/sigma/a7469) (Ala/A)89.10C3H7NO2C3H5NO71.082.349.69–6.00 [Arginine](https://www.sigmaaldrich.com/US/en/product/sigma/a8094) (Arg/R)174.20C6H14N4O2C6H12N4O156.192.179.0412.4810.76 [Asparagine](https://www.sigmaaldrich.com/US/en/product/sigma/a7094) (Asn/N)132.12C4H8N2O3C4H6N2O2114.112.028.80–5.41 [Aspartic acid](https://www.sigmaaldrich.com/US/en/product/sigma/a9256) (Asp/D)133.11C4H7NO4C4H5NO3115.091.889.603.652.77 [Cysteine](https://www.sigmaaldrich.com/US/en/product/sial/c6852) (Cys/C)121.16C3H7NO2SC3H5NOS103.151.9610.288.185.07 [Glutamic acid](https://www.sigmaaldrich.com/US/en/product/sigma/g8415) (Glu/E)147.13C5H9NO4C5H7NO3129.122.199.674.253.22 [Glutamine](https://www.sigmaaldrich.com/US/en/product/sigma/g8540) (Gln/Q)146.15C5H10N2O3C5H8N2O2128.132.179.13–5.65 [Glycine](https://www.sigmaaldrich.com/US/en/product/sigma/g7126) (Gly/G)75.07C2H5NO2C2H3NO57.052.349.60–5.97 [Histidine](https://www.sigmaaldrich.com/US/en/product/sial/h8000) (His/H)155.16C6H9N3O2C6H7N3O137.141.829.176.007.59 [Hydroxyproline](https://www.sigmaaldrich.com/US/en/search/isoleucine?focus=products&page=1&sort=relevance&term=isoleucine&type=product) (Hyp/O)131.13C5H9NO3C5H7NO2113.111.829.65–– [Isoleucine](https://www.sigmaaldrich.com/US/en/product/sigma/i7403) (Ile/I)131.18C6H13NO2C6H11NO113.162.369.60–6.02 [Leucine](https://www.sigmaaldrich.com/US/en/product/sigma/l8912) (Leu/L)131.18C6H13NO2C6H11NO113.162.369.60–5.98 [Lysine](https://www.sigmaaldrich.com/US/en/product/sigma/l8662) (Lys/K)146.19C6H14N2O2C6H12N2O128.182.188.9510.539.74 [Methionine](https://www.sigmaaldrich.com/US/en/product/sigma/m5308) (Met/M)149.21C5H11NO2SC5H9NOS131.202.289.21–5.74 [Phenylalanine](https://www.sigmaaldrich.com/US/en/product/sigma/p5482) (Phe/F)165.19C9H11NO2C9H9NO147.181.839.13–5.48 [Proline](https://www.sigmaaldrich.com/US/en/product/sigma/p5607) (Pro/P)115.13C5H9NO2C5H7NO97.121.9910.60–6.30 Pyroglutamatic (Glp/U)139.11C5H7NO3C5H5NO2121.09–––5.68 [Serine](https://www.sigmaaldrich.com/US/en/product/sigma/s4311) (Ser/S)105.09C3H7NO3C3H5NO287.082.219.15–5.68 [Threonine](https://www.sigmaaldrich.com/US/en/product/sigma/t8441) (Thr/T)119.12C4H9NO3C4H7NO2101.112.099.10–5.60 [Tryptophan](https://www.sigmaaldrich.com/US/en/product/sigma/t8941) (Trp/W)204.23C11H12N2O2C11H10N2O186.222.839.39 –5.89 [Tyrosine](https://www.sigmaaldrich.com/US/en/product/sigma/t8566) (Tyr/Y)181.19C9H11NO3C9H9NO2163.182.209.1110.075.66 [Valine](https://www.sigmaaldrich.com/US/en/product/sigma/v0513) (Val/V)117.15C5H11NO2C5H9NO99.132.329.62–5.96 1 pKa is the negative of the logarithm of the dissociation constant for the -COOH group. 2 pKb is the negative of the logarithm of the dissociation constant for the -NH3 group. 3 pKx is the negative of the logarithm of the dissociation constant for any other group in the molecule. 4 pl is the pH at the isoelectric point. Reference: D.R. Lide, *Handbook of Chemistry and Physics*, *72nd Edition*, CRC Press, Boca Raton, FL, 1991. * * * ## [](https://www.sigmaaldrich.com)Amino Acids by Side Chain Amino acids are the compounds or building blocks that make up peptides and proteins. Each amino acid is structured from an amino group and a carboxyl group bound to a tetrahedral carbon. This carbon is designated as the α-carbon (alpha-carbon).  Amino acids differ from each other with respect to their side chains, which are referred to as R groups. The R group for each of the amino acids will differ in structure, electrical charge, and polarity. Refer to the charts and structures below to explore amino acid properties, types, applications, and availability. - [Hydrophobic - aliphatic](https://www.sigmaaldrich.com#ali) - [Hydrophobic - aromatic](https://www.sigmaaldrich.com#aro) - [Neutral - polar side chains](https://www.sigmaaldrich.com#neu) - [Acidic](https://www.sigmaaldrich.com#acid) - [Basic](https://www.sigmaaldrich.com#basic) - [Unique](https://www.sigmaaldrich.com#unique) * * * ## Amino Acids with Hydrophobic Side Chain – Aliphatic ![Alanine, Ala, A](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/ala.gif "Alanine, Ala, A") [Alanine, Ala, A](https://www.sigmaaldrich.com/product/sigma/a7469) ![Isoleucine, Ile, I](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/Ile.gif "Isoleucine, Ile, I") [Isoleucine, Ile, I](https://www.sigmaaldrich.com/product/sigma/i7403) ![Leucine, Leu, L](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/leu.gif "Leucine, Leu, L") [Leucine, Leu, L](https://www.sigmaaldrich.com/product/sigma/l8912) [](#) ![Methionine, Met, M](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/met.gif "Methionine, Met, M") [Methionine, Met, M](https://www.sigmaaldrich.com/product/sigma/m5308) ![Valine, Val, V](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/val.gif "Valine, Val, V") [Valine, Val, V](https://www.sigmaaldrich.com/product/sigma/v0513) [](#) [](#) * * * ## Amino Acids with Hydrophobic Side Chain – Aromatic ![Phenylalanine, Phe, F](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/phe.gif "Phenylalanine, Phe, F") [Phenylalanine, Phe, F](https://www.sigmaaldrich.com/product/sigma/p5482) ![Tryptophan, Trp, W](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/trp.gif "Tryptophan, Trp, W") [Tryptophan, Trp, W](https://www.sigmaaldrich.com/product/sigma/t8941) ![Tyrosine, Tyr, Y](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/tyr.gif "Tyrosine, Tyr, Y") [Tyrosine, Tyr, Y](https://www.sigmaaldrich.com/product/sigma/t8566) [](#) * * * ## Amino Acids with Polar Neutral Side Chains ![Asparagine, Asn, N](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/asn.gif "Asparagine, Asn, N") [Asparagine, Asn, N](https://www.sigmaaldrich.com/product/sigma/a7094) ![Cysteine, Cys, C](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/cys.gif "Cysteine, Cys, C") [Cysteine, Cys, C](https://www.sigmaaldrich.com/product/sial/c6852) ![Glutamine, Gln, Q](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/gln.gif "Glutamine, Gln, Q") [Glutamine, Gln, Q](https://www.sigmaaldrich.com/product/sigma/g8540) [](#) ![Serine, Ser, S](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/ser.gif "Serine, Ser, S") [Serine, Ser, S](https://www.sigmaaldrich.com/product/sigma/s4311) ![Threonine, Thr, T](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/thr.gif "Threonine, Thr, T") [Threonine, Thr, T](https://www.sigmaaldrich.com/product/sigma/t8441) [](#) [](#) * * * ## Amino Acids with Electrically Charged Side Chains – Acidic ![Aspartic acid, Asp, D](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/asp.gif "Aspartic acid, Asp, D") [Aspartic acid, Asp, D](https://www.sigmaaldrich.com/product/sigma/a9256) ![Glutamic acid, Glu, E](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/glu.gif "Glutamic acid, Glu, E") [Glutamic acid, Glu, E](https://www.sigmaaldrich.com/product/sigma/g8415) [](#) [](#) * * * ## Amino Acids with Electrically Charged Side Chains – Basic ![Arginine, Arg, R](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/arg.gif "Arginine, Arg, R") [Arginine, Arg, R](https://www.sigmaaldrich.com/product/sigma/a8094) ![Histidine, His, H](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/his.gif "Histidine, His, H") [Histidine, His, H](https://www.sigmaaldrich.com/product/sial/h8000) ![Lysine, Lys, K](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/lys.gif "Lysine, Lys, K") [Lysine, Lys, K](https://www.sigmaaldrich.com/product/sigma/l8662) [](#) * * * ## Unique Amino Acids ![Glycine, Gly, G](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/gly.gif "Glycine, Gly, G") [Glycine, Gly, G](https://www.sigmaaldrich.com/product/sigma/g7126) ![Proline, Pro, P](https://www.sigmaaldrich.com/content/dam/cms-commons/sigmaaldrich/marketing/global/images/technical-documents/articles/protein-biology/protein-structural-analysis/pro.gif "Proline, Pro, P") [Proline, Pro, P](https://www.sigmaaldrich.com/product/sigma/p5607) [](#) [](#) * * * ## [](https://www.sigmaaldrich.com)[](https://www.sigmaaldrich.com)Hydrophobicity Index for Common Amino Acids The hydrophobicity index is a measure of the relative hydrophobicity, or how soluble an amino acid is in water. In a protein, hydrophobic amino acids are likely to be found in the interior, whereas hydrophilic amino acids are likely to be in contact with the aqueous environment. The values in the table below are normalized so that the most hydrophobic residue is given a value of 100 relative to glycine, which is considered neutral (0 value). The scales were extrapolated to residues which are more hydrophilic than glycine. | | | | | |----------------------|-----|-----|-----------------| | At pH 2A | | | At pH 7B | | __Very Hydrophobic__ | | | | | Leu | 100 | Phe | 100 | | Ile | 100 | Ile | 99 | | Phe | 92 | Trp | 97 | | Trp | 84 | Leu | 97 | | Val | 79 | Val | 76 | | Met | 74 | Met | 74 | | __Hydrophobic__ | | | | | Cys | 52 | Tyr | 63 | | Tyr | 49 | Cys | 49 | | Ala | 47 | Ala | 41 | | __Neutral__ | | | | | Thr | 13 | Thr | 13 | | Glu | 8 | His | 8 | | Gly | 0 | Gly | 0 | | Ser | -7 | Ser | -5 | | Gln | -18 | Gln | -10 | | Asp | -18 | | | | __Hydrophilic__ | | | | | Arg | -26 | Arg | -14 | | Lys | -37 | Lys | -23 | | Asn | -41 | Asn | -28 | | His | -42 | Glu | -31 | | Pro | -46 | Pro | -46 (used pH 2) | | | | Asp | -55 | ApH 2 values: Normalized from Sereda et al., *J. Chrom.* 676: 139-153 (1994). BpH 7 values: Monera *et al*., *J. Protein Sci.* 1: 319-329 (1995). ### References 1\. Hayman M, Smith K, Cameron N, Przyborski S. 2005. Growth of human stem cell-derived neurons on solid three-dimensional polymers. Journal of Biochemical and Biophysical Methods. 62(3):231-240. [https://doi.org/10.1016/j.jbbm.2004.12.001](https://doi.org/10.1016/j.jbbm.2004.12.001) 2\. Cho IJ, Ahn JY, Kim S, Choi MS, Ha TY. 2008. Resveratrol attenuates the expression of HMG-CoA reductase mRNA in hamsters. Biochemical and Biophysical Research Communications. 367(1):190-194. [https://doi.org/10.1016/j.bbrc.2007.12.140](https://doi.org/10.1016/j.bbrc.2007.12.140) 3\. Polleux F, Ghosh A. 2002. The Slice Overlay Assay: A Versatile Tool to Study the Influence of Extracellular Signals on Neuronal Development. Science Signaling. 2002(136):pl9-pl9. [https://doi.org/10.1126/stke.2002.136.pl9](https://doi.org/10.1126/stke.2002.136.pl9) 4\. Rama Rao KV, Reddy PV, Tong X, Norenberg MD. 2010. Brain Edema in Acute Liver Failure. The American Journal of Pathology. 176(3):1400-1408. [https://doi.org/10.2353/ajpath.2010.090756](https://doi.org/10.2353/ajpath.2010.090756) 5\. Marx M, Günter RH, Hucko W, Radnikow G, Feldmeyer D. 2012. Improved biocytin labeling and neuronal 3D reconstruction. Nat Protoc. 7(2):394-407. 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