Due to the extensive use of xylooligosaccharides (XOS) as functional food ingredients,many inferior goods and even adulterants are generally found in the market,which may pose a health hazard to certain populations.Chromatography method such as high-performance liquid chromatography (HPLC) and high-performance thin-layer chromatography (HPTLC) is traditionally applied for the quality analysis of XOS.However,it is time consuming due to the prolonged separation and pre-or post-derivatization procedure.In this study,a fast saccharide mapping method based on matrix-assisted laser desorption/time-of-flight mass spectrometry (MALDI-TOF-MS) was developed for the quality consistency analysis of 22 batches of XOS collected from different manufacturers in China.The time needed for saccharides analysis using MALDI-MS was less than 30 min for one plate,at least 6 times faster than that by the traditional HPTLC chromatography method.In addition,MALDI-MS possessed higher resolution for XOS with DP4-DP7 based on the difference of m/z,which is hardly separated using HPTLC.The results showed that XOS were present only in samples XY01-XY11,samples XY12-XY14 only consisted of hex oligo-saccharides,and samples XY15-XY22 were free of oligosaccharides.These indicate that the quality consistency of XOS products in the China market was poor,which should be carefully investigated.

Objective To investigate the relationship between urinary iodine level and prevalence of thyroid disease by comparing the levels of urinary iodine in patients with thyroid disease and healthy people in Hefei urban residents.Methods A prospective study was used in the study.A total of 238 patients with thyroid disease were enrolled in the Third Affiliated Hospital of Anhui Medical University from March 2015 to January 2017,and these patients were divided into three groups:Graves's disease (GD) group (n =116),chronic lymphocyticthyroiditis (HT) group (n =79) and thyroid nodule group (n =43),568 cases of Hefei urban residents without thyroid disease were selected as control group Urinary iodine was measured by arsenic-cerium catalyzed spectrophotometry.Thyroid stimulating hormone (TSH),free triiodothyronine (FT3),free thyroxine (FT4),thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb) were measured by chemiluminescence immunoassay.The thyroid was examined through B ultrasonography in both the case group and the control group.Results The median urinary iodine concentrations(MUIC) of GD group,HT group,thyroid nodule group and control group were 326.83,361.49,235.26,and 195.63 μg/L,there were significant differences in the MUIC between the 4 groups (H =20.13,P ＜ 0.05).The MUIC of GD group and HT group were higher than that of control group (Z =5.395,6.269,P ＜ 0.05).The MUIC was significantly different between the HT group and the thyroid nodule group (Z =3.852,P ＜ 0.05).There were significant differences in TSH,FT3,FT4,TPOAb,TgAb between the GD group and the control group (P ＜ 0.05);the TPOAb and TgAb in the HT group and thyroid nodule group were statistically significantly different compared with those of control group (P ＜ 0.05).There was no correlation between the level of urinary iodine level and FT3,FT4,TSH,TPOAb and TgAb in the 4 groups (P ＞ 0.05).Conclusions According to the urinary iodine level in the normal population,the Hefei urban area belongs to the area of appropriate iodine.There was no corrolation between urinary iodine level and thyroid function in urban residents of Hefei.

3-Phosphoglycerate dehydrogenase (PGDH, EC 1.1.1.95) is the key enzyme in L-serine biosynthesis and its coding gene is serA. PGDH is feedback inhibited by L-serine. In order to relieve the feedback-inhibition of PGDH by L-serine, H344 or D346 or D364 were chosen for site directed mutagenesis. The mutants were generated by the standard QuikChange mutagenesis, further subcloned into expression vector pT7-7 and transformed into Escherichia coli BL21 (DE3) cells. The recombinant cells were collected after cultured in LB media post induced by isopropyl beta-Dthiogalactopyranoside. The enzymes were purified by anion exchange chromatography, and SDS-PAGE showed that the purified enzymes were homogenous. Enzyme characterization indicated that the mutant enzyme showed similar activity, optimal temperature, and optimal pH as that of the wild-type enzyme. Moreover, feedback inhibition study showed that the activity of the double mutant (N346A/H344A) could remain 96% in the presence of serine up to 160 mmol/L, whereas the activity of the wild-type enzyme remains only 50% in the presents of serine of 7 μmol/L, thus successfully relieving the feedback inhibition of PGDH with its activity remained.
Electrophoresis, Polyacrylamide Gel ; Escherichia coli ; enzymology ; Escherichia coli Proteins ; genetics ; Industrial Microbiology ; Mutagenesis, Site-Directed ; Phosphoglycerate Dehydrogenase ; genetics ; Serine ; biosynthesis

Rhus chinensis is an important economic species, which could provide raw materials for pharmaceutical and industrial dyes. Rhus chinensis is famous for its resistance to drought, cold, and salt. It grows in temperate, warm temperate, and subtropical regions. We report here Rhus chinensis chloroplast genomes by de novo sequencing. The results show that the length of Rhus chinensis was 159 082 bp, exhibiting a typical four-part structure with two single-copy regions (long single copy [LSC] and short single copy [SSC] sections) separated by a pair of inverted repeats (IRs). The length of LSC and SSC was 85 394 bp and 18 663 bp, respectively. The genomes contained 126 genes, including 88 protein encoding genes, 8 rRNA and 30 tRNA genes. In the chloroplast genome, 61.97% of the sequence were gene coding region. In the sequence of gene encoding region, the vast majority of sequences were protein encoding region, accounting for 86.65%, followed by rRNA (10 620 bp, 10.77%) and tRNA (2 540 bp, 2.58%). In Rhus chinensis chloroplast genome, only 8 genes contain introns, all containing 1 intron except ycf3 gene (2 introns). The Rhus chinensis chloroplast genome contains 755 SSR locies. SSR mainly consists of dinucleotide and mononucleotide, accounting for 60% (453) and 28.74% (217) respectively. The clustering results show that Anacardiaceae were closest to Rhus chinensis, followed by Aceraceae and Sapindaceae. This study provides a molecular basis for the classification of Rhus chinensis.
Genome, Chloroplast ; genetics ; Open Reading Frames ; Phylogeny ; Rhus ; classification ; genetics ; Sequence Analysis, DNA