GLOSSARY

Agarose:

A polysaccharide with many hydroxyl groups. The material can be used to construct gels to separate nucleic acid fragments.

Ampholytes:

A mixture of polycarboxylic and polyamino acids.

Antibody:

A molecule that recognizes a specific antigen or antigenic epitope.

Antigen:

A molecule that can be recognized by a specific antibody. Antigens are often proteins but can also include other types of macromolecules such as DNA or lipids. Different types of immunoassays exploit this property thus to detect and/or quantify antigens in cells, tissues and body fluids.

Antigenic determinant:

See epitope.

Azocasein:

An orange azo dye covalently bound to the milk protein casein, which provides a substrate for peptidases which cleave peptide bonds within the three-dimensional structure of a protein.

Bacilli:

Rod-shaped bacteria (singular - bacillus). An example is Bacillus megaterium.

bis:

Occurring twice, as in bis-acrylamide or bis-tris-propane.

Centrioles:

Cylindrical structures that nucleate the formation of microtubules in eukaryotic cells and form the poles of the mitotic spindle.

Chelating agent:

A compound (e.g. EDTA) which preferentially binds to metal ions. This reduces or effectively eliminates the metal ions' presence in a solution.

Clathrate:

(caged in a lattice) A chemical structure where a compound is trapped within a lattice structure of another compound.

Cocci:

Round or spherical-shaped bacteria (singular - coccus). An example is Micrococcus luteus.

Collimate:

To make parallel.

Confidence interval:

A confidence interval for a set of values describes the likely range within which a specific value can be considered to be part of the same population or data set. Increasing the degree of confidence with which this assumption can be made (e.g. from 95 to 99%) will increase the limits of the range and vice versa. This measure is often used in clinical research, as it describes the likely range of expected values for a particular treatment or condition. See also 'confidence limits'.

Confidence limits:

A statistical term for the pair of values that describe the upper and lower end of a range of values within which a value can be expected to fall for a given level of confidence. In other words, the two values are the end points of the confidence interval.

Dalton:

The mass of a reagent relative to 1/12 the mass of carbon, i.e. 1.0.

Dialysis:

A means to separate components in a solution by unequal diffusion through a semipermeable membrane.

Dynodes:

One of a series of electrodes in a photomultiplier.

ELISA:

Abbreviation for 'enzyme-linked immunosorbent assay', which is an antibody-based assay in which antigen (one-site ELISA) or antibody (two-site ELISA) are typically immobilized on a solid support matrix, such as a microtiter plate. Enzyme-linked secondary antibodies are used to detect antigen-antibody binding.

Endoplasmic reticulum:

A specialized membranous organelle within eukaryotic cells responsible for synthesis of membrane proteins and lipids.

Epitope:

The specific part of an antigen that is recognized by an antibody. In the case of protein antigens, this could be a short sequence of consecutive amino acids in the protein antigen's primary structure. However, epitopes with chemical modifications of protein-bound amino acids (e.g. phosphorylation of tyrosine, serine and threonine residues, acetylation of lysine residues, and polyglutamylation) can also be detected by some antibodies.

Eukaryotes:

Organisms that are composed of one or more cells which contain a membrane-enclosed nucleus and organelles (e.g. animal, plant, fungi, yeast and most algae).

Fab fragment:

Fragment antibody binding can be released by limited proteolysis of an immunoglobulin molecule; it contains the antigen binding site and comprises one constant and one variable domain of each of the heavy and light chains.

Fc fragment:

Fragment crystallizable is a fragment of an immunoglobulin molecule which can be released by limited proteolysis; it contains the 'effector region', which binds to Fc receptors on the cell surface of certain types of cells of the immune system or to proteins of the complement system thus facilitating activation of the immune system. It is the part of primary antibodies that is typically targeted by labelled secondary antibodies in immunoassays. It comprises heavy chain constant regions from both heavy chains.

Fluorophore:

A molecule that emits fluorescence at a specific wavelength (emission wavelength) when irradiated with an appropriate wavelength of electromagnetic radiation (excitation wavelength). They may be used to detect the levels of specific molecules to which they bind, or they may be covalently linked to proteins such as antibodies and used in the detection of specific antigens in immunoassays.

Focal plane:

The plane perpendicular to the lens' optical axis in which images of points in the object field of the lens are in focus.

Glycogen:

A storage form of glucose in animal cells. Often present as cytoplasmic granules, which are particularly abundant in liver cells.

Golgi apparatus:

A specialized organelle within the cytoplasm of eukaryotic cells that is involved in the glycosylation of membrane proteins and secretory proteins.

Gravity:

The natural weak force of attraction that exists between all bodies in the universe (g = 981 cm s-2).

Heavy constant (HC):

A highly conserved sequence in the immunoglobulin heavy chain

Heavy variable:

A sequence in the immunoglobulin heavy chain containing hypervariable regions involved in antigen binding.

Homogenate:

A tissue or cellular mixture resulting from the action of a homogenizer.

Homogenizer:

A laboratory machine that disrupts tissue (cells) by shearing, cutting and blending the starting material in a buffer.

Hydrophilic:

('water loving') A molecule (functional group) which prefers to interact with water or other polar solvents.

Hydrophobic:

('water hating') A molecule (functional group) which avoids contact with water or other polar solvents.

Immiscible:

Incapable of mixing together (e.g. oil and water).

Immunoassays:

Assays that exploit the use of antibodies to detect and/or quantify specific antigens in cells, tissues and body fluids.

Immunoglobulin:

Proteins produced by circulating B cells and various types of white cells, which assist in the immune response (e.g. during infection). Different classes of immunoglobulins exist and have distinct roles in the immune systems. Antibodies are immunoglobulin molecules that can be produced and purified for use in immunoassays, whereas circulating immunoglobulins can assist in the immune response and/or represent useful biomarkers of diseases.

Intermediate filaments:

Filaments of 10 nm width made of various proteins (e.g. desmin in muscle cells, nuclear lamins in the nuclear lamina). These filaments play a structural role in eukaryotic cells.

In vitro:

Literally means 'in glass'.

In vivo:

Literally means 'in life'.

Isoelectric point (pI):

The pH value at which a zwitterionic molecule (e.g. an amino acid or protein) carries no net charge. The molecule will not move under the influence of an electrical field or bind to ion exchange resins.

I.U.:

International units of enzyme activity defined as 1µmol of product formed (or substrate consumed) min-1 at a given temperature (usually 25 °C).

Light constant (LC):

A highly conserved sequence in the immunoglobulin light chain.

Light variable (LV):

A sequence in the immunoglobulin light chain containing hypervariable regions involved in antigen binding.

Lyophilization:

(freeze drying) The removal of water from a solution or tissue after freezing in a vacuum, where the water sublimes from the solid phase to the gas phase without entering the liquid phase.

Lysosomes:

Single membrane bounded organelles in eukaryotic cells that contain hydrolytic enzymes. These enzymes (e.g. acid phosphates) are maintained in an acidic pH environment within the organelle, where they can degrade macromolecules in a controlled manner.

Mean:

The arithmetic average of a set of values.

Median:

The exact midpoint of a set of values or observations.

Meniscus:

The curved shape assumed by a liquid in a cylindrical tube.

Microfilaments:

Polymers of 5 nm width made from the protein actin. Important in contractile processes (e.g. thin filaments in muscle...