Polar and Nonpolar Amino Acids
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Polar and Nonpolar Amino Acids

Amino acids are a class of amphoteric organic compounds containing alkaline amino groups and acidic carboxyl groups. They are the basic building blocks of biological functional macromolecule proteins. Amino acids can be divided into protein amino acids and non-protein amino acids. Among them, protein amino acids are also called standard amino acids, which are amino acids that directly participate in the synthesis of protein molecules. According to the different positions of the amino group on the carbon chain, amino acids can be divided into α-, β-, γ- and other amino acids, but the amino acids that make up natural proteins in the biological world are all α-amino acids, a total of 22 types, including 20 common amino acids and 2 uncommon amino acids. Non-protein amino acids cannot directly participate in the synthesis of protein molecules and need to be modified to participate in the synthesis of proteins, such as citrulline, ornithine and hydroxyproline. Amino acids have different properties due to their different structures, R groups, etc., such as isoelectric point, optical rotation, etc.

amino acid structure

  • Amino group (-NH2): This is a basic group with two hydrogen atoms and one nitrogen atom, which gives amino acids certain basic properties.
  • Carboxyl group (-COOH): This is an acidic group containing one carbon atom, two oxygen atoms and one hydrogen atom, which gives amino acids acidic properties.
  • Side chain (R group): The specific properties of each amino acid mainly depend on its unique side chain (or side group), which is a hydrocarbon chain or ring structure containing different elements and functional groups. The difference in side chains determines the difference between the 20 common amino acids and affects their functions and interactions in organisms.

These 20 amino acids have their own genetic codes. They are the building blocks of biosynthetic proteins and have no species differences. According to the polarity of the side chain R, they can be divided into non-polar and polar amino acids. If R is only H or C and H, it is hydrophobic; if it contains polar side chain groups, such as -OH, -SH, -COOH, -NH2, etc., then the amino acid is polar.

Polar Amino Acids

Polar amino acids are a class of organic compounds that are the basic building blocks of proteins and enzymes in living organisms. These amino acids are characterized by the presence of polar functional groups, such as hydroxyl (-OH), amino (-NH2), and carboxyl (-COOH) groups, which make them water-soluble and able to form hydrogen bonds with other molecules. There are seven polar amino acids in the standard genetic code: serine (Ser), threonine (Thr), asparagine (Asn), glutamine (Gln), tyrosine (Tyr), cysteine (Cys), and arginine (Arg). Each of these amino acids plays a unique role in protein structure and function, and they are essential for the normal functioning of cells and tissues in the body. According to the nature of the R group, polar amino acids can be divided into:

  • Polar Neutral Amino Acids

The R group is polar, but does not dissociate, or only dissociates very weakly, and their R groups are hydrophilic. Such as: serine, threonine, cysteine, tyrosine, glutamine, asparagine.

  • Polar Charged Amino Acids

Polar charged amino acids can be divided into polar amino acids with positive charge and polar amino acids with negative charge. Polar amino acids with positive charge are also called basic amino acids. The R group is polar and dissociated. They are acidic in neutral solution and have strong hydrophilicity. Examples include aspartic acid and glutamic acid. Polar amino acids with negative charge are also called acidic amino acids. The R group is polar and dissociated. They are alkaline in neutral solution and have strong hydrophilicity. Examples include histidine, lysine and arginine.

Which Amino Acids are Polar?

BOC Sciences is a leading supplier of amino acid compounds for research, pharmaceutical, and industrial applications. We are committed to quality and customer satisfaction, offering amino acids in a wide range of purities and forms to meet the various needs of our customers. At BOC Sciences, we understand the critical importance of amino acids in biological processes and chemical synthesis. With our extensive selection of amino acid compounds, researchers and industry professionals can obtain the materials they need to advance their work and achieve successful results. We have a very extensive list of polar amino acids for customers to choose from (including but not limited to):

CatalogProduct NameCAS NumberCategoryInquiry
BAT-002155O-Trityl-L-serine25840-83-9L-Amino AcidsInquiry
BAT-002805Boc-L-serine3262-72-4BOC-Amino AcidsInquiry
BAT-003373Z-L-serine1145-80-8CBZ-Amino AcidsInquiry
BAT-003722Fmoc-D-serine116861-26-8Fmoc-Amino AcidsInquiry
BAT-003598DL-Threonine80-68-2DL-Amino AcidsInquiry
BAT-002736Boc-D-threonine55674-67-4BOC-Amino AcidsInquiry
BAT-000461Nα-Z-L-asparagine2304-96-3CBZ-Amino AcidsInquiry
BAT-002718Boc-D-glutamine61348-28-5BOC-Amino AcidsInquiry
BAT-003290Z-D-glutamine13139-52-1CBZ-Amino AcidsInquiry

Non Polar Amino Acids

Nonpolar amino acids, also known as hydrophobic amino acids, are characterized by the absence of charged or polar groups in their side chains. Instead, these amino acids have relatively simple side chain structures consisting mainly of hydrocarbon groups. The hydrophobicity of nonpolar amino acids stems from the fact that water molecules are polar and hydrogen bond, which makes it energetically unfavorable for them to interact with nonpolar molecules. Therefore, nonpolar amino acids tend to cluster inside proteins, away from the surrounding water environment. Non-polar neutral amino acids include glycine, alanine, valine, leucine, isoleucine, methionine, phenylalanine, tryptophan, and proline.

Which Amino Acids are Nonpolar?

One of the main advantages of BOC Sciences is that our amino acid compounds are available in a variety of purity grades, from analytical to pharmaceutical grade, to ensure that researchers can obtain the purity level required for their specific applications. We also provide custom synthesis services for customers who need amino acid compounds that are not available in our catalog. Our experienced team of chemists and scientists can work with customers to develop custom synthesis solutions to meet their specific requirements. In addition to our standard amino acid compound catalog, BOC Sciences also offers a variety of formats to meet different research and manufacturing needs, including powders, liquids and solid forms, as well as solutions and custom formulations. Our non-polar amino acids mainly include but are not limited to:

CatalogProduct NameCAS NumberCategoryInquiry
BAT-005541Fmoc-β-(3-thienyl)-D-alanine220497-90-5Fmoc-Amino AcidsInquiry
BAT-005543Fmoc-β-chloro-L-alanine212651-52-0Fmoc-Amino AcidsInquiry
BAT-003452Phthaloyl-glycine4702-13-0Cyclic Amino AcidsInquiry
BAT-003623Trifluoroacetyl glycine383-70-0DL-Amino AcidsInquiry
BAT-015488Glutamyl-Valine5879-06-1OthersInquiry
BAT-015684L-Propyl-L-valine52899-09-9OthersInquiry
BAT-003590DL-Leucine328-39-2DL-Amino AcidsInquiry
BAT-003641Fmoc-D-leucine114360-54-2Fmoc-Amino AcidsInquiry

Polar vs Nonpolar Amino Acids

Polar and nonpolar amino acids have different properties that affect their solubility, interactions, and function in proteins. The balance between polar and nonpolar amino acids is critical to maintaining protein stability and function in living organisms. The table below compares the charge, stability, solubility, and protein interactions of polar and nonpolar amino acids.

CharacteristicsPolar Amino AcidsNon-Polar Amino Acids
ChargeCan be positively charged, negatively charged, or neutral.Neutral in charge.
Hydrogen BondingCan form hydrogen bonds with polar molecules, including water and other polar amino acids.Cannot form hydrogen bonds with polar molecules.
SolubilityGenerally soluble in water.Generally insoluble in water.
Location in ProteinsOften found on the surface of proteins.Usually buried inside proteins.
ReactivityMore reactive due to its hydrophilicity.Low reactivity due to hydrophobicity.
Specific examplesSerine, threonine, asparagine, lysine, arginine, glutamine, aspartic acid.Alanine, valine, leucine, isoleucine, phenylalanine, tryptophan, methionine.
Function in proteinsOften involved in protein-protein interactions, enzymatic reactions, and ligand binding.Usually involved in maintaining the stability of protein structure.

What is the Medical Use of Amino Acids?

Amino acids are mainly used in medicine to prepare compound amino acid infusions, and are also used as therapeutic drugs to synthesize peptide drugs. There are more than a hundred amino acids used as drugs, including 22 amino acids that constitute proteins and more than 100 amino acids that constitute non-proteins. Compound preparations composed of multiple amino acids occupy a very important position in modern intravenous nutrition infusions and dietary supplements. In addition, amino acids such as glutamic acid, arginine, aspartic acid, cystine, and L-dopa can already act alone to treat some diseases, mainly for the treatment of liver diseases, gastrointestinal diseases, encephalopathy, cardiovascular disease, respiratory diseases, as well as for improving muscle vitality, pediatric nutrition and detoxification. In addition, amino acid derivatives have shown promise in cancer treatment.

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