Acyl radical -- A chemical group radical in which a carbon-oxygen pair is bonded to a partner in place of the typical hydroxyl group.

Affinity chromatography -- A laboratory technique developed in 1951 by Dan Hampston Campbell, an immunologist at the California Institute of Technology. Affinity chromatography refers to the use in chromatography of particular materials as adsorbents of groups which are supposed to be specific ligands of the protein being purified. Through this process, Anfinsen could analyze the fragments of the three-dimensional amino acid chain.

Alpha-amylase -- An enzyme that degrades starch; amylase removes two glucose residues at a time, leaving the starch chain shorter.

Amino acid -- The basic building block of proteins and polypeptides; containing a basic amino group, an acidic carboxyl group, and a side chain attached to an alpha carbon atom, and that link together by peptide bonds to form proteins, or that function as chemical messengers and as intermediates in metabolism.

Antibody -- Any of the protein molecules produced by specialized immune system cells (B cells) that can recognize and bind to a particular foreign antigen. If the antigen is on the surface of a cell, this binding leads to cell aggregation and subsequent destruction. Antibodies are also referred to as immunoglobulins.

Beta-galactosidase -- The enzyme that splits lactose into glucose and galactose.

Biochemistry, or biological chemistry -- The study of the chemical substances and vital processes occurring in living organisms; "the chemistry of life," or the study of the structure and properties of molecules in living organisms and how those molecules are made, changed, and broken down.

Bioengineering, or biomedical engineering -- The application of engineering principles to the fields of biology and medicine, as in the development of aids or replacements for defective or missing body organs, or in the development of certain genetic treatments.

Carbohydrate -- Any of a group of organic compounds that includes sugars, starches, celluloses, and gums and serves as a major energy source in the diet of animals. These compounds are produced by photosynthetic plants and contain only carbon, hydrogen, and oxygen, with twice as many hydrogen atoms as oxygen atoms.

Chymotrypsin -- A protease that catalyses the hydrolysis (the breakdown) of proteins into peptides or amino acids in the small intestine. It is selective for peptide bonds with aromatic or large hydrophobic side chains on the carboxyl side of this bond. Chymotrypsin also catalyses the hydrolysis of ester bonds.

Chymotrypsinogen -- The inactive proenzyme secreted by the pancreas that is subsequently converted to chymotrypsin.

Circular dichroism -- A spectroscopic method which measures the difference in absorbance of left- and right-handed circularly polarized light by a material, as a function of the wavelength.

Cistron -- A basic unit of hereditary material, it is the smallest genetic unit that must be intact to function as a transmitter of genetic information, i.e., to determine the sequence of amino acids of one polypeptide chain. By one definition, it is synonymous with "gene."

Covalent bond -- A chemical bond that involves sharing of electron pairs.

Cysteine -- A sulfur-containing nonessential amino acid produced by the enzymatic or acid hydrolysis of proteins. It is easily oxidized to cystine.

Disulfide interchange enzyme -- An enzyme that catalyzes the rearrangement of disulfide bonds within proteins during folding.

DNA, or deoxyribonucleic acid -- The primary genetic material of all cellular organisms and the DNA viruses. Located predominantly in cell nuclei, it is composed of two chains of nucleotides--deoxyribose and phosphate backbones with side chains of purine (adenine or guanine) or pyrimidine (cytosine and thymine) bases projecting inward. Hydrogen bonds link adenine to guanine, and cytosine to thymine. The two linked strands are twisted in a double helix.

Endoplasmic reticulum -- An extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome studded, or rough, and ribosome free, or smooth, regions.

Fluorescence -- Emission of light by excited molecules as they revert to the ground state.

Genotype -- The specific allelic composition of a cell, either of the entire cell or more commonly for a certain gene or a set of genes. Also, the genes an organism possesses.

Glutamic acid -- A nonessential amino acid occurring in proteins. It also serves as an excitatory neurotransmitter in all regions of the central nervous system.

Glutamine -- The monoamide of glutamic acid, a nonessential amino acid occurring in the juices of many plants and some animal tissues; it is an important carrier of urinary ammonia and is broken down in the kidney by the enzyme glutaminase.

Half-cystine -- One-half of a cystine (a white crystalline amino acid formed from the disulfide linkage of two cysteines during folding of many proteins and stabilizing the tertiary structure of the protein) molecule or of a cystinyl residue in a protein or peptide.

Histochemistry -- The branch of science that deals with the chemical composition of the cells and tissues of the body.

Immunology -- The branch of biomedicine concerned with the structure and function of the immune system, innate and acquired immunity, the bodily distinction of self from nonself, and laboratory techniques involving the interaction of antigens with specific antibodies.

In vitro -- An experimental situation outside a living cell or organism; biological or chemical work done in the test tube, instead of in living systems. "In vitro" is Latin for "in glass."

In vivo -- An experimental situation in a living cell or organism; biological or chemical work done in living systems.

Interferon -- A family of small proteins that stimulate viral resistance in cells.

Ligand -- A molecule that binds specifically to another molecule. Usually, it refers to a small molecule that binds specifically to a larger one.

Lipoproteins -- Any of a group of conjugated proteins in which at least one of the components is a lipid. These proteins are the principal means by which lipids are transported in the blood.

Lysozome -- A membrane-bound organelle in the cytoplasm of most cells containing various hydrolytic enzymes that function in intracellular digestion.

Lysozyme -- A basic enzyme present in saliva, tears, egg white, and many other animal fluids. It functions as an antibacterial agent. The enzyme catalyzes the hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in peptidoglycan and between N-acetyl-D-glucosamine residues in chitodextrin.

Major histocompatibility complex (MHC) -- The genetic region which contains the loci of genes which determine the structure of the genes (serologically and lymphocyte-defined transplantation antigens) which control the structure of the immune response-associated antigens (the immune response genes which control the ability of an animal to respond immunologically to antigenic stimuli).

Mercaptoethanol -- A water soluble thiol not of biological origin. It is used in biochemistry to cleave disulphide bonds in proteins or to protect sulphydryl groups from oxidation.

Metastable -- An unstable and transient, but relatively long-lived, state of a chemical or physical system, as of a supersaturated solution or an excited atom.

Microsome -- A small particle in the cytoplasm of a cell typically consisting of fragmented endoplasmic reticulum to which ribosomes are attached.

Monospecific antibody -- A species of antibody able to react with only a single specified antigen or antigenic determinant.

Myoglobin -- A single-chain, iron-containing protein found in muscle fibers, structurally similar to a single subunit of hemoglobin and having a higher affinity for oxygen than hemoglobin of the blood.

Noncovalent bond -- A bond in which electrons are not shared between atoms.

Nucleic acid -- A large molecule composed of nucleotide subunits.

Nucleotide -- A unit that polymerizes into nucleic acids (DNA or RNA). Each nucleotide consists of a purine (adenine or guanine) or pyrimidine (cytosine, thymine, or uracil) base, a sugar (ribose in the case of RNA, deoxyribose in the case of DNA), and a phosphate molecule.

Peptide bond -- A bond joining two amino acids.

Phenotype -- The form taken by one or a group of characteristics in a specific individual; the detectable outward manifestations of a specific genotype.

Plasma -- The watery fluid portion of blood in which the corpuscular elements are suspended. It transports nutrients and wastes throughout the body.

Plasmodium knowlesi -- A protozoan parasite native to Southeast Asia that causes "monkey malaria" and which can easily be passed to man.

Polypeptide -- A chain of linked amino acids; a protein.

Protein -- A large molecule composed of one or more chains of amino acids in a specific order. The order is determined by the base sequence of nucleotides in the gene that codes for the protein. Proteins are required for the structure, function, and regulation of the body's cells, tissues, and organs. Each protein has unique functions.

Protein folding -- A rapid biochemical reaction involved in the formation of proteins. It begins even before a protein has been completely synthesized and proceeds through discrete intermediates before the final structure is developed.

Renaturation -- The process by which proteins or complementary strands of nucleic acids re-form their native conformations.

RNA, or ribonucleic acid -- A single-stranded nucleic acid found in the cell nucleus and cytoplasm, which plays a key role in protein synthesis. (It also constitutes the genetic material of the RNA viruses.) It is similar to DNA but has ribose sugar, rather than deoxyribose sugar, and uracil, rather than thymine, as one of the pyrimidine bases. There are several classes of RNA molecules, including messenger RNA, transfer RNA, and ribosomal RNA, each serving a different purpose in the cell.

RNase, or Ribonuclease -- Any nuclease specifically catalyzing the cleavage of phosphate ester linkages in ribonucleic acids. Ribonucleases are grouped as those cleaving internal bonds, the endoribonucleases, and those cleaving at termini, the exoribonucleases.

Staphylococcus aureus -- Commonly called "staph," this bacterium produces a poison/toxin that is the most common cause of foodborne illness. Because of its relative structural simplicity and ease of reproduction, it has been a commonly used organism for genetic research.

Spectrofluorometry -- The measurement of the intensity and quality of fluorescence, or the emission of electromagnetic radiation (especially of visible light) by a substance stimulated with the absorption of incidental radiation.

Thermostable, or thermostability -- Unaffected by relatively high temperatures, as certain ferments or toxins.

Tyrosyl -- The acyl radical of tyrosine.