Lab 4: Spectrophotometry and Bradford Assay

Electromagnetic spectrum

Range of all types of electromagnetic radiation.

Spectrophotometer

Device measuring light absorption in solutions.

Absorbance (A)

Amount of light absorbed by a sample.

Transmittance (t)

Ratio of transmitted light through a sample.

Beer's Law

A = (ab) C; relates absorbance to concentration.

Cuvette

Optical glass or quartz test tube for samples.

Coomassie Blue

Dye used in Bradford Assay for proteins.

Extinction coefficient

Quantifies a substance's absorptivity at a wavelength.

Path length (b)

Distance light travels through the sample.

Standard curve

Graph relating absorbance to known concentrations.

Percent transmittance (%T)

Transmittance multiplied by 100%.

Optical density

Another term for absorbance, unit-less measure.

Wavelength (λ)

Distance between successive peaks of light waves.

Incubation time

Minimum 20 minutes for dye and samples.

Linear relationship

Direct proportionality between absorbance and concentration.

Unknown sample

Sample with unknown concentration to be measured.

Stock solution

Concentrated solution used to prepare standards.

Dilution

Process of reducing concentration by adding solvent.

Photomultiplier tube

Converts light into an electric current.

Absorptivity

Substance's ability to absorb specific wavelengths.

Standard concentrations

Known values used to create a standard curve.

Calibration

Process of adjusting the spectrophotometer for accuracy.

Absorption data

Measurements collected to determine concentrations.

Correlation coefficient (R²)

Statistical measure of how well data fits a model.

Bovine Gamma Globulin (BGG)

Protein used as a standard in assays.

Bovine Serum Albumin (BSA)

Common protein standard for concentration assays.

Visible light

Part of the spectrum detectable by human eyes.