Method/Service

Result

Notes

AAA

Determination of free amino acids or of the protein concentration in a sample. Recovered amino acids are usually reported in picomoles and nanograms recovered.

Presently this is considered to be the most accurate method for the determination of amino acids and protein contents.

However, matrix effects due to interfering compounds in the formulation buffer are possible. In the case of formulated proteins, sometimes the method only works accurately if the protein is highly purified prior to the analysis.

Electroblotting

A picture of the membrane containing the protein band(s) is reported.

Needed for N-terminal Sequencing.

HPLC

Detection of the purity of a biological compound, small molecule, amino acid, peptide or protein often as a single peak. A typical HPLC report includes a chromatogram showing a single peak or, in the case when impurities are present, multiple peaks.

Analytical run to determine purity and to estimate amounts of peptides, proteins or other compounds of interest. However, for proteins, the measurement of exact concentrations is not possible unless a control protein with the exact sequence and protein folding and modification is available for establishing a calibration curve. Similarly, for other biomolecules an accurate standards are needed as well for a quantitative analysis.

LC-MS/MS

Protein sequence identification is done from gel pieces or protein pellets containing the protein(s) of interest via tryptic digest, and LC-MS/MS analysis followed by database searches. Often nano-spray-LC-MS/MS is used to achieve more sensitive results.

Protein identification via mass pattern matching. The N-terminal and C-terminal end may be present in the data. However it is possible that the N- and C-terminal are missing.

MALDI-MS

This type of analysis will result in a mass measurement of a compound such as a carbohydrate, lipid, oligo-nucleotide, peptide or protein. Mass spectra with the observed peaks are usually reported.

This analysis is more accurate than molecular weight determination via SDS-PAGE. Impurities originating from peptides and protein fragments or other sources are observed as well.

N-terminal sequencing

For X cycles. A typical report will contain the observed sequence plus the chromatogram of the cycles done.

This method will provide sequence information starting from the N-terminal end of the protein. Sometimes up to 40 or 45 cycles may be observed. However, in the earlier days of protein sequencer development up to 60 or even 75 cycles were reported.

SDS-PAGE

Usually a picture of a 1D gradient gel is reported showing the apparent molecular weights.

Removes PBS and sugars from oligonucleotides, peptides, and proteins.

UV absorbance at 280 nm

The absorbance of the protein at 280 nm is measured and reported. A BSA standard curve can be used to estimate the specific absorbance.

Unless the specific absorbance is known this will only give an estimate of the protein concentration.