(gen.) The taking in, incorporation or reception of gases, liquids, light or heat.
(phys/chem) Penetration of one substance into the inner structure of another (cf. adsorption, in which one substance is attracted and held on the surface of another). Occurs between a gas or vapor and a liquid.
(pharm.) The process of movement of a drug from the site of application into the extracellular compartment of the body.

Microorganism (Mycoplasma) used in sterility testing of < 0.1 µm-rated filters.

A hydrogen containing compound which itself or its solution has an acidic pH (< 7.0) and which can react with a base to form a salt.

The region of a protein molecule which binds the specific substrate and chemically modifies it (in an enzyme) or interacts with it (in a receptor).

Retention of gas, liquid, solid or a dissolved substance on a surface due to positive interaction (attraction) between the surface and the molecules of the adsorbed material. The interactive forces can be electrostatic (coulombic) or nonelectrostatic (dipole-dipole and hydrophobic). Adsorption to a membrane or filter device can occur in a specific manner (affinity) or nonspecifically.

This term is applied to organisms which grow in the presence of oxygen. An organism which requires oxygen to grow is termed an obligate aerobe.

Generally refers to the ability that two molecules have to bind to each other. It is typically measured in a binding assay where increasing amounts of one molecule is added until the binding sites are saturated. The concentration of the variable molecule that achieves half of the saturation value is called the Kd (binding constant) and is a direct measure of the strength of binding. The stronger the affinity the higher the Kd. When researchers refer to affinity purification they are usually talking about the use of an antibody to catch and purify a specific protein.

A polysaccharide plant product isolated from red algae. It is used as a gelling agent and also to make solid media for the growth of microorganisms.

Agarose is a purified component of agar, a naturally occurring high molecular weight polysaccharide obtained from red algae. It forms highly porous yet rigid gels, which are used as stabilizing media for electrophoresis of DNA and RNA. The nucleic acids can be recovered from the gel using Nanosep® and Nanosep MF devices.

A method used to separate, identify and purify molecules of different weight and/or structure. It is specifically applied to the separation of DNA fragments. It is a rapid, simple and accurate process. The separated molecules can be visualized directly by staining with dyes. The electrophoretic migration rate of molecules through agarose gel is dependent on the following parameters:

1. molecular size: molecules pass through the gel at rates that are inversely proportional to the log of their molecular weight.
2. agarose concentration: a molecule of a given size migrates at different rates through gels containing different concentrations of agarose.
3. molecular conformation: a molecule of the same molecular weight but of a different conformation will migrate at different rates. Generally closed circular or globular forms will migrate faster than linear forms.
4. electric current: at low voltages, the rate of migration is proportional to the voltage, but as the voltage is increased the rate of migration of high molecular weight fragments is increased differentially. See Electrophoresis.

The sticking together of insoluble antigens such as bacteria, viruses, or erythrocytes caused by a specific antibody. Agglutination assays are used to type human blood before a transfusion.

An organic compound containing a -OH group. Often alcohol can be used as a sanitization agent by treating a sample with 70% ethanol. Alcohols that are miscible in water (such as methanol, ethanol, or isopropanol) can be used to prewet a hydrophobic membrane (such as PTFE) prior to filtration of an aqueous liquid. They can also be used to verify the integrity of membrane filters with small pores.

A representative sample of a larger quantity.

An amphoteric molecule or substance, such as amino acid or protein. Ampholytes can ionize to form either cations (acids) or anions (bases) because they have both acidic (proton donor) and basic (proton acceptor) groups. The sum of charges carried by these groups determines the net charge of the molecule. There is a pH called the isoelectric point (pl), at which the sums of negative and positive charges are equal and the molecule has zero net charge.

See Ampholyte. Capable of acting both as an acid and as a base. Amphoteric membranes may contain positive and negatively charged surface groups but carry a net neutral charge (for example, Biodyne® A membrane).

An antibiotic widely used in clinical treatment and rDNA research. It is a derivative of penicillin which kills bacteria by interfacing with the synthesis of the cell wall.

Literally, "life without air." This term is applied to organisms which do not require oxygen to grow and for which oxygen is toxic. An organism which requires the absence of oxygen is termed an obligate anaerobe.

In drug discovery, it is a molecule that is able to bind to the same site as another molecule. This ability is often due to structural similarities between the molecules. Often analogs are added in increasing concentrations to a binding assay in order to confirm that the binding is truly specific. The half-saturation level of binding inhibition seen by adding analogs is called the Ki (inhibition constant) and is a measure of the relative affinities of the two molecules.

Any molecule that is measured by physical, chemical or biological means.

When a salt is dissolved it has two charged molecules: a cation (positively charged) which can behave as an acid and an anion (negatively charged) which can act as a base. If a surface has a positive charge it is called anionic and can be used to capture negatively charged molecules.

A membrane in which the pore size and structure are not the same throughout the thickness of the membrane. Such membranes are usually considered "directional" because of the difference in flow characteristics depending on which side of the membrane faces the feed stream.

Positive pole or electrode of an electrolytic system. Anionic molecules are attracted to the anode.

Any of a group of substances which has the ability to kill or weaken bacteria.

Antibodies are proteins (immunoglobulins) synthesized by the immune system in response to an antigen. They are Y-shaped, with a "tail" and two "arms." The arms have a unique shape that enables them to combine specifically with the antigen. This plays an important role in the body’s defense against infection (bacteria, viruses) or other foreign protein substances. The specificity of the antibody-antigen reaction forms a basis for highly specific and sensitive immunoassays. They can be used to purify specific molecules from a mixed solution using affinity.

A foreign substance (usually proteinaceous or high molecular weight polysaccharide) which induces the formation of antibodies. Examples are bacteria, viruses, endo/exotoxins, pollen and vaccines.

The blood serum obtained from an animal after it has been immunized with a particular antigen. It will contain antibodies which are specific for that antigen as well as antibodies specific for any other antigens, against which the animal has previously been immunized.

Similar to or resembling water. In reference to solution made in water.

For life sciences, an array is usually a series of spots of a collection of molecules that are arranged on a membrane in a very specific pattern. A second labeled molecule or probe can be used to detect binding or hybridization to a particular spot. The address of that spot indicates which molecule is present in the complex mixture. Gene expression profiles are commonly analyzed using hybridization arrays. Dot blots and "gene chips" are examples of arrays.

Refers to an operation performed in a sterile environment or using appropriate precautions (such as flaming pipettes) designed to prevent contamination through introduction of bacteria.

Analytical procedure to determine purity, concentration, or biological activity of a specific substance in a mixture. In drug discovery, an assay is performed to determine the relative affinity that a ligand has for its respective target.

A chamber for sterilizing filters or equipment with saturated steam by using constant high temperature and pressure (121 °C, 15 psi). Many materials requiring sterilization (such as cell culture media and injectable drugs) are degraded by the heat of an autoclave and must be sterilized by other means, such as filtration.

A technique for imaging an object which has been radiolabeled, by exposing a photographic film to the object itself. Used to detect the location of transferred DNA fragments on a membrane (such as Biodyne® or BioTrace™ membranes) which have hybridized with radiolabeled probes. The photographic image generated by this process is called an Autoradiogram. Recently the same procedures have been used to detect chemiluminescent probes.

AKA streptavidin. A molecule found in egg whites which has a high affinity for the molecule biotin. This strong and specific binding property is used widely in molecular biology for labeling and detection. One molecule can be attached to an avidin molecule and a second molecule can be bound to biotin. When mixed, the two molecules are now bound together through the action of the avidin and biotin allowing two molecules that do not normally interact to be forced into proximity. Like antibodies, these molecules can be used for affinity purification.