Optimization of low-abundance protein extraction and abundant protein removal from defatted soybean meal.

The aim of this study was to optimize the conditions for the extraction of low-abundance proteins (LAPs) and the removal of abundant proteins (APs; ß-conglycinin and glycinin) from soybean meal. Single factor and orthogonal experiments were designed to determine the effects of four factors (isopropanol concentration, total extraction time, ultrasonic power, and ultrasonic time) on protein concentration in isopropanol extracts. Proteins in the isopropanol supernatant and the cold acetone precipitate of isopropanol were identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS). The results showed that the optimal conditions were 50% isopropanol, ultrasonic pretreatment for 15 min at 350 W, and a total extraction time of 1 h. Under these conditions, the protein concentration in the isopropanol extracts reached 0.8081 g/L. Many LAPs were detected, including ß-amylase, soybean agglutinin, soybean trypsin inhibitor, fumarylacetoacetase-like, phospholipase D alpha 1-like, oleosin, and even some unknown soybean proteins. The soybean APs (ß-conglycinin and glycinin) were not found. The method may be useful for discovering new soybean proteins and extracting enough LAPs of soybean to allow further studies of their physiological effects on animals without the influence of APs.

[Significance of serum vascular endothelial growth factor test before radiotherapy in patients with nasopharyngeal carcinoma].

OBJECTIVE: To study the changes of serum vascular endothelial growth factor (VEGF) and beta 2-microglobulin levels before and after radiotherapy in 58 patients with nasopharyngeal carcinoma (NPC), and to elucidate the clinical significance of VEGF and beta 2-microglobulin test before radiotherapy. METHODS: Serum VEGF level was measured by sandwich ELISA in 58 patients with NPC and 24 healthy individuals, and the serum beta 2-microglobulin was assayed with time-resolved fluoroimmunoassay. RESULTS: The serum VEGF level in patients with NPC was (174.0+/-130.0) ng/L, higher than (134.1+/-66.6) ng/L of the healthy subjects, but the difference was not significant (P>0.05). The serum VEGF level was higher in T4 and IV a patients with NPC. No significant differences in the levels of serum VEGF were found among various N classifications in the patients with NPC. Patients with the serum VEGF level higher than 267.3 ng/L (mean+2 s of the serum VEGF level in the healthy individuals) had a shorter metastasis-free survival time (P<0.05). Although the patients with high beta 2-microglobulin level had a shorter survival time, the difference was not significant. CONCLUSION: The NPC patients with high serum VEGF level have a poor prognosis.