Laboratory techniques for biologists

Hazard

a substance organism or piece of equipment in a laboratory that can cause harm

Laboratory hazards

toxic and corrosive chemicals heat and flammable substances pathogenic organisms and mechanical equipment

Risk

the likelihood of harm arising from exposure to a hazard

Risk assessment

the process of identifying possible risks and the control measures used to minimise them

Control measures

methods used to reduce risk including appropriate handling techniques protective clothing and equipment and aseptic technique

Linear dilution series

a dilution series in which concentrations differ by an equal interval such as 0.1 M 0.2 M 0.3 M

Log dilution series

a dilution series in which concentrations differ by a constant proportion such as 10⁻¹ 10⁻² 10⁻³

Standard curve

a graph produced by plotting measured values for known concentrations to determine the concentration of an unknown solution

Buffer

a solution that resists changes in pH when small amounts of acid or alkali are added

Colorimeter

an instrument used to quantify the concentration and turbidity of a solution

Colorimeter calibration

the use of an appropriate blank to set a baseline measurement

Absorbance

a colorimeter measurement used to determine the concentration of a coloured solution using suitable wavelength filters

Percentage transmission

a colorimeter measurement used to determine the turbidity of a solution

Centrifugation

a technique used to separate substances of differing density by spinning

Pellet

the more dense components that settle at the bottom of a centrifuge tube

Supernatant

the less dense components that remain above the pellet after centrifugation

Paper chromatography

a technique used to separate substances such as amino acids and sugars

Thin layer chromatography

a chromatography technique using a coated plate to separate substances

Chromatography solute movement

the distance travelled by a solute depends on its solubility in the solvent

Affinity chromatography

a separation technique in which target proteins bind to specific molecules in a column while non-target molecules are washed out

Gel electrophoresis

a technique used to separate proteins and nucleic acids

Electrophoresis principle

charged macromolecules move through a gel matrix in an electric field

Native gel electrophoresis

a technique that separates proteins and nucleic acids by shape size and charge

Native gels

gels that do not denature molecules so separation depends on shape size and charge

SDS-PAGE

an electrophoresis technique that denatures proteins and gives them equal negative charge so they separate by size only

Isoelectric point (IEP)

the pH at which a protein has no net charge and precipitates out of solution

Isoelectric precipitation

separation of proteins by adjusting pH so only proteins with a specific IEP precipitate

Isoelectric focusing

separation of soluble proteins using an electric field and a pH gradient gel

Protein migration in IEF

a protein stops moving at its IEP because it has no net charge

Antibody detection

proteins can be detected using specific antibodies

Immunoassay

a technique that uses monoclonal antibodies to detect and identify specific proteins

Monoclonal antibodies

antibodies with identical specificity produced from a single clone of cells

Antibody label

a chemical label attached to an antibody specific to the protein antigen

Reporter systems

labels that produce a detectable signal such as colour change chemiluminescence fluorescence or radioactivity

Antigen-based assays

immunoassays that use a specific antigen to detect the presence of antibodies

Western blotting

a technique in which proteins separated by SDS-PAGE are transferred to a solid membrane

Western blot detection

proteins on the membrane are identified using specific antibodies with reporter enzymes

Bright-field microscopy

a technique used to observe whole organisms tissues thin sections or individual cells

Fluorescence microscopy

a technique using fluorescent labels to visualise specific molecules or structures

Aseptic technique

procedures used to eliminate unwanted microbial contamination during culture

Aseptic procedure

sterilisation of equipment and media followed by exclusion of contaminants

Microbial culture initiation

starting a culture using an inoculum on agar or in nutrient broth

Culture media

nutrient formulations that promote growth of specific cells or microbes

Animal cell culture medium

medium containing serum-derived growth factors

Growth factors

proteins that stimulate cell growth and proliferation

Cell line division capacity

primary cell lines divide a limited number of times while tumour cell lines divide indefinitely

Plating out

spreading diluted microbial culture on solid media to count colonies

Colony-forming units (CFUs)

colonies arising from individual viable microbial cells

Serial dilution

repeated dilution used to obtain a countable number of colonies

Haemocytometer

a device used to estimate cell numbers in a liquid culture

Vital staining

staining used to identify and count viable cells