SINGLE-STEP ELECTROTRANSFER OF REVERSE-STAINED PROTEINS FROM SODIUM DODECYL SULFATE-POLYACRYLAMIDE GEL ONTO REVERSED-PHASE MINICARTRIDGE AND SUBSEQUENT DESALTING AND ELUTION WITH A CONVENTIONAL HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY GRADIENT SYSTEM FOR ANALYSIS
C. Fernandezpatron et al., SINGLE-STEP ELECTROTRANSFER OF REVERSE-STAINED PROTEINS FROM SODIUM DODECYL SULFATE-POLYACRYLAMIDE GEL ONTO REVERSED-PHASE MINICARTRIDGE AND SUBSEQUENT DESALTING AND ELUTION WITH A CONVENTIONAL HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY GRADIENT SYSTEM FOR ANALYSIS, Electrophoresis, 16(6), 1995, pp. 911-920
Isolation of proteins from polyacrylamide electrophoresis gels by a no
vel combination of techniques is described. A given protein band from
a reverse stained (imidazol-sodium dodecyl sulfate - zinc salts) gel c
an be directly electrotransferred onto a reversed-phase chromatographi
c support, packed in a self-made minicartridge (2 mm in thickness, 8 m
m in internal diameter, made of inert polymeric materials). The minica
rtridge is then connected to a highperformance liquid chromatography s
ystem and the electrotransferred protein eluted by applying an acetoni
trile gradient. Proteins elute in a small volume (< 700 mu L) of high-
purity volatile solvents (water, trifluoroacetic acid, acetonitrile) a
nd are free of contaminants (gel contaminants, salts, etc). Electrotra
nsferred proteins were efficiently retained, e.g., up to 90% for radio
iodinated alpha-lactalbumin, by the octadecyl matrix, and their recove
ry on elution from the minicartridge was in the range typical for this
type of chromatographic support, e.g., 73 % for a-lactalbumin. The te
chnique was successfully applied to a variety of proteins in the molec
ular mass range 6-68 kDa, and with amounts between 50 and 2000 pmol. T
he good mechanical and chemical stability of the developed minicartrid
ges, during electrotransfer and chromatography, allowed their repeated
use. This new technique permitted a single-step separation of two pro
teins unresolved by sodium dodecyl sulfate-polyacrylamide gel electrop
horesis due to their different elution from the reversed-phase support
. The isolated proteins were amenable to analysis by N-terminal sequen
cing, enzymic digestion and mass spectrometry of their proteolytic fra
gments. Chromatographic elution of proteins from the reversed-phase mi
ni-cartridge was apparently independent of the specific loading mode e
mployed, i.e., loading by conventional loop injection or by electrotra
nsfer.