Gel Filtration Chromatographic Methods Research Articles

Development and validation of an analytical method to ensure quality requirements of hydrolysed proteins intended for agricultural use as biostimulants

Plant biostimulants, as defined by EU Reg.1009/2019, represent a promising solution to increase agricultural production, improving the efficiency of fertilizers and thus reducing their environmental impact. At present, protein hydrolysates are considered the main class of biostimulants as they increase yield and product quality of various crops. Several sources of proteins are used to produce protein hydrolysates, but in this context of environmental protection and green economy, the development of biostimulants from industry by-products is of great interest. Industry by-products of animal origin (ABPs) are classified into three categories based on the degree of risk for animal, human and environmental health, according to EU Reg. 1069/2009. In particular, tanneries are known to produce large quantities of Category 3 ABPs, which are associated with no health risk. According to EU Reg. 142/2011, ruminant proteins derived from ABPs Category 3 must be hydrolysed to a molecular weight below 10.000 Daltons (Da). This research aims to set up and validate an analytical method for a reliable determination of the high limit molecular weight of hydrolysed proteins derived from Category 3 ABPs. A gel filtration chromatography method was developed and validated by evaluation of linearity, repeatability, reproducibility (intermediate precision) and measurement uncertainty. The validation process was carried out according to Eurachem and ISO guidelines and performance characteristics were further verified by testing the method in a second and independent laboratory. Acceptance criteria of linearity R2>0.990, repeatability RSD%≤5, intermediate repeatability RSD%≤10 and uncertainty measurement U ≤ 20% were met. Therefore, the method was considered suitable to assess the compliance of the hydrolysed proteins to 10.000 Da limit in biostimulants from animal by-products.

Seed Protein from Artocarpus hirsutus Lam. with Trypsin Inhibitory, Micro-bicidal and Antioxidant Activities Induces Depletion of Human Skin Cancer (A431) and Colon Cancer (HT29) Cells

: Natural trypsin inhibitors are increasingly recognised as putative anticancer or antimicrobial therapeutics. In the present study, we isolated a proteinaceous trypsin inhibitor from the seeds of Artocarpus hirsutus to assess its anticancer, antioxidant and microbicidal effects. A trypsin inhibitory protein (AhTI) was isolated from the seeds of A. hirsutus using ion exchange and gel filtration chromatographic methods. The trypsin inhibitory activity of AhTI was confirmed by activity staining using Reverse Zymography. The effect of AhTI on human cancer cell lines (A431 and HT29) was studied by microscopic examination, MTT assay and LDH leakage analysis. Antioxidant activity of AhTI was analysed by ferric reducing power and DPPH radical scavenging assays. An agar well diffusion method was used to check the antimicrobial activity of AhTI. The purification protocols used in the study significantly increased the specific activity of the target protein from 72.65 ± 0.86 to 2048 ± 27.3. AhTI offers significant activity against the proliferation of the A431 and HT29 cancer cell lines. In vitro AhTI shows potent antioxidant activity and exhibits antimicrobial activity against all the bacteria and fungi isolates used in this study. Of particular note, AhTI was particularly effective against Staphylococcus aureus and Escherichia coli. This in vitro study shows that AhTIis a promising candidate for further development novel therapeutics targeting cancer, microbial infections and oxidative stress.

Extraction, Purification and Characterization of β-Galactosidase from Tomato (Lycopersicom esculentum)

β-galactosidase enzyme EC (3.2.1.23), lactase, can be described as an enzyme of glycoside hydrolase which performs the catalyzing of β-galactosidas hydrolysis to monosaccharides by breaking glycosidic bond. The objective of this study was to extraction and purification β-galactosidase from tomato (Lycopersicom esculentum.), ten Different types of extraction were investigated to selection of the best extraction of the enzyme, The Na. phosphate buffer (0.1M and pH6) had given a highest Specific activity of crude enzyme has been 212.27 U/mg. protein. The purification procedures were performed with the use of the precipitation of ammonium sulfate, Ion-exchange and gel filtration chromatographic techniques. ammonium sulfate (70) % saturation has been the best method for precipitation and partially purification of enzyme with a purification fold 1.83 and enzymatic yield 88.31%. This followed by the use of ion exchange chromatography by DEAE sephadex A50 column, the purification times of the enzymatic extract were 2.36, with an enzymatic yield 25.48%. After the final purification step of gel filtration chromatography using SephadexG-100 column, the enzyme has been purified 3.92 fold with 16.33% of enzymatic yield. The optimum enzymatic activity was found at pH (6). The plant extracts tomato (Lycopersicom esculentum) were used to characterize the enzyme in the term of pH, temperature,. The enzyme activity measured by its ability to hydrolyze the substrate 2-nitrophenyl β-D-galactopyranoside (ONPG). The enzyme activity was reached maximum at 45°C and at pH 5.5. The enzyme’s molecular weight has been estimated to 74 KDa by the gel filtration chromatography method, and 73 k D on SDS-PAGE.

Optimization of a Screening Method for Macroprolactinemia

ObjectiveTo optimize a screening method for macroprolactinemia and improve the accuracy of free prolactin (freePRL) detection. MethodOverall efficiency, calculated as the product of the immunoglobulin G (IgG) precipitation rate and the freePRL recovery rate were employed to determine the concentration of the precipitant polyethylene glycol (PEG). Then, an optimized screening method for macroprolactinemia was established. The concentrations of freePRL, obtained by gel filtration chromatography (GFC), from 66 cases were used as the gold standard, and the sensitivity, specificity, accuracy and precision of the optimized and traditional methods for detecting macroprolactinemia were compared. Results(1) The IgG precipitation rate increased with increasing PEG6000 concentration, and the freePRL recovery rate decreased with increasing PEG6000 concentration; the overall efficiency first increased and then decreased. When the IgG concentrations in the mixture were 10 g/L, 25 g/L and 40 g/L, the concentrations of PEG6000 with the highest overall efficiency were 24%, 20% and 18%, respectively. (2) The effect of high and low IgG on the overall efficiency was 4.7% when using 20% PEG6000, which was lower than the effects when using 18% or 24% PEG6000 (9.2% and 13.2%). (3) In the optimized method established using 20% PEG6000, the macroprolactin (macroPRL) chromatographic peak disappeared, but the freePRL chromatographic peak was retained. The sensitivity of this macroprolactinemia screening method was 96.7%, and the specificity was 100%. (4) The freePRL concentrations obtained by the optimized method for samples from 30 macroprolactinemia cases and 36 true hyperprolactinemia cases were 15.8 (10.2-21.4) ng/mL and 60.2 (51.8-79.9) ng/mL; the concentrations were similar to those obtained using the GFC method (16.3 (11.9-27.2) ng/mL and 68.1 (49.5-92.9) ng/mL, respectively (p > 0.05)) and higher than those obtained using the traditional method (9.1 (6.1-17.6) ng/mL and 51.4 (43.7-71.9) ng/mL), respectively, p < 0.05)). (5) The relative deviation between the optimized and GFC methods was -7.0%, which was significantly lower than the relative deviation between the traditional and GFC methods (-21.4%, p < 0.01). (6) The in-batch coefficients of variation (CVs) for the dual-level quality control materials measured by the optimized method were 1.88% and 1.87%, and the within-laboratory CVs were 2.55% and 2.29%, which were slightly lower than the in-batch CVs (1.93% and 2.81%) and within-laboratory CVs (2.75% and 2.81%) measured by the traditional method. ConclusionThe established optimized method for screening macroprolactinemia using 20% PEG6000 as a precipitant can completely precipitate macroPRL components and effectively retain freePRL components. Compared with traditional methods, the optimized method is simpler, more accurate and more stable for the quantitative detection of freePRL.

Purification and Characterization of Alpha Toxin Clostridium perfringens Type A

Clostridium perfringens is a toxin-producing anaerobe with the ability to cause multiple diseases in humans and animals. One of the toxins produced by all strains of this bacterium is an alpha toxin (phospholipase C). This study aimed to purify and characterize alpha-toxin. C. perfringens type A was grown in an optimized medium, the culture supernatant was separated, and ammonium sulfate precipitated protein was subjected to ion exchange and gel filtration chromatography methods. The purification steps were monitored by SDS-PAGE and hemolysin activity for each sample and performed by the hemolysin assay method. The purified alpha-toxin appeared in a single band in 43 KDa. The enzymatic efficiency yield was about 88% with a specific activity of 69170 and 654 fold of purification. According to the results, alpha-toxin is Zn and Mg metal-enzyme dependent on the temperature and pH optimum of 40 °C and 6, respectively. The enzyme Km and Vmax values of 3.8 mg/ml and 0.19 were calculated as the enzyme in the presence of lecithin. The partially purified alpha toxin with specific characters can be used for different applications such as antibody production and determination of the anti-toxin rate in animal serum.

Inhibitor effect of PCMB and PMSF towards partially purified product from pineapple core (Ananas comosus [L.] Merr) using gel filtration column chromatography method

The research aims to isolate, purify, and examine the inhibitors effect of a partially purified product from pineapple core with Palembang type pineapple (Ananas comosus [L.] Merr). The isolation process obtained crude enzymes with specific activity 42.60 Units/mg. Purification of crude enzymes using fractionation method with ammonium sulfate obtained bromelain fraction with the highest specific activity at 0–50 % saturation level of ammonium sulfate, which is 230.22 Units/mg with a purity level of 5.40 times from its crude extract. Further purification of 0–50 % ammonium sulfate fraction by gel filtration chromatography method using DEAE-Sephadex G-50 matrix obtained enzyme with specific activity 275.46 Units/mg with purity level 6.50 times from its crude extract. The optimum substrate concentration was at a concentration of 1.0 % (w/v). The purified bromelain has a Michaelis-Menten (Km) constant value and the maximum speed of the enzymatic reaction (Vmax) i.e. 0.52 % (w/v) and 0.51 Units/min. The proteolytic activity of bromelain is strongly inhibited by PCMB compound and activated by PMSF at 0.1 mM concentration of 67.27 %.

Biochemical insights into the recombinant 10-deacetylbaccatin III-10-β-O-acetyltransferase enzyme from the Taxol-producing endophytic fungus Lasiodiplodia theobromae.

10-deacetylbaccatin III-10-β-O-acetyltransferase (DBAT) is a key rate-limiting enzyme of the Taxol biosynthetic pathway, which is uncharacterized in Taxol-producing endophytic fungi. Here, an open reading frame of DBAT was cloned from the Taxol-producing endophytic fungus Lasiodiplodia theobromae (LtDBAT). The LtDBAT enzyme was heterologously expressed and purified by the affinity and gel filtration chromatography methods. The molecular weight of the purified protein was 49 kDa and its identity was confirmed by western blot. The purified LtDBAT enzyme was capable of catalyzing 10-deacetylbaccatin III into baccatin III, as shown by liquid chromatography-mass spectroscopy. The mass spectra of baccatin III were identical to the authentic baccatin III. The LtDBAT enzyme was characterized and the kinetic parameters of catalysis were determined. In addition, localization of LtDBAT was performed by using confocal microscopy and the result showed that the enzyme was localized in lipid droplets. Together, this study provides biochemical insights into the fungal recombinant DBAT enzyme that is involved in the Taxol biosynthetic pathway. In the near future, engineering of the LtDBAT enzyme and the Taxol biosynthetic pathway in endophytic fungi could be an eco-friendly and economically feasible alternative source for production of Taxol and its precursors.

Purification and Characterization of Xylanases from the Fungus Chrysoporthe cubensis for Production of Xylooligosaccharides and Fermentable Sugars.

Xylanases from the pathogen fungus Chrysoporthe cubensis were produced under solid state fermentation (SSF) using wheat bran as carbon source. The enzymatic extracts were submitted to ion exchange (Q Sepharose) and gel filtration chromatography methods (Sephadex S-200) for purification. The xylanases were divided into three groups: P1 showed better performance at 60°C and pH 4.0, P2 at 55°C and pH3.0, and P3 at 80°C and pH 3.0. Oat spelt xylan was the best substrate hydrolyzed by P1 and P3, while beechwood xylan was better degraded by P2. Carboxymethyl cellulose (CMC) and p-nitrophenyl-β-D-xylopyranoside (p-NPβXyl) were not hydrolyzed by any of the xylanases. The K M' or K M values, using oat spelt xylan as substrate, were 2.65mg/mL for P1, 1.81mg/mL for P2, and 1.18mg/mL for P3. Xylobiose and xylotriose were the main xylooligosaccharides of oat spelt xylan degradation, indicating that the xylanases act as endo-β-1,4-xylanases. Xylanases also proved to be efficient for hydrolysis of sugarcane bagasse when used as supplement of a commercial cocktail due to the increase of the reducing sugar release.

Metal binding activity of pectin isolated from seagrass Zostera marina and its derivatives

Low esterified pectin was isolated from the seagrass Zostera marina. Dynamics of the isolation process for the pectin from this seagrass was investigated. Two pectin derivatives: galacturonide (A) with molecular weight 30.55 kDa and galacturonide (B) with molecular weight 3.94 kDa were obtained using acidic hydrolysis of the native pectin from Zostera marina. Molecular weight parameters (Mw, Mn, Mw/Mn) of this pectin and its derivatives as well as of commercial apple pectin were determined using gel-filtration chromatography method. Comparative assessment of Cd2+, Pb2+, Y3+-binding activity of the native Zostera pectin, galacturonides A and B, and commercial apple pectin was performed. The results showed that galacturonide A with molecular weight 30.55 kDa possesses highest metal-binding capacity and may be considered as a candidate for development of medicines with metal-binding activity.

Production of Extremely Alkaliphilic, Halotolerent, Detergent, and Thermostable Mannanase by the Free and Immobilized Cells of Bacillus halodurans PPKS-2. Purification and Characterization

The alkaliphilic Bacillus halodurans strain PPKS-2 was shown to produce extracellular extreme alkaliphilic, halotolerent, detergent, and thermostable mannanase activity. The cultural conditions for the maximum enzyme production were optimized with respect to pH, temperature, NaCl, and inexpensive agro wastes as substrates. Mannanase production was enhanced more than 4-fold in the presence of 1% defatted copra meal and 0.5% peptone or feather hydrolysate at pH11 and 40°C. Mannanase was purified to 10.3-fold with 34.6% yield by ion exchange and gel filtration chromatography methods. Its molecular mass was estimated to be 22kDa by SDS-PAGE. The mannanase had maximal activity at pH11 and 70°C. This enzyme was active over a broad range of NaCl (0-16%) and thermostable retaining 100% of the original activity at 70°C for 3h. Immobilization of whole cells proved to be effective for continuous production of mannanase. Since the strain PPKS-2 grows on cheaper agro wastes such as defatted copra meal, corn husk, jowar bagasse, and wheat bran, these can be exploited for mannanase production on an industrial scale.

Structural and Biophysical Characterization of the Interactions between the Death Domain of Fas Receptor and Calmodulin

The extrinsic apoptotic pathway is initiated by cell surface death receptors such as Fas. Engagement of Fas by Fas ligand triggers a conformational change that allows Fas to interact with adaptor protein Fas-associated death domain (FADD) via the death domain, which recruits downstream signaling proteins to form the death-inducing signaling complex (DISC). Previous studies have shown that calmodulin (CaM) is recruited into the DISC in cholangiocarcinoma cells, suggesting a novel role of CaM in Fas-mediated signaling. CaM antagonists induce apoptosis through a Fas-related mechanism in cholangiocarcinoma and other cancer cell lines possibly by inhibiting Fas-CaM interactions. The structural determinants of Fas-CaM interaction and the underlying molecular mechanisms of inhibition, however, are unknown. Here we employed NMR and biophysical techniques to elucidate these mechanisms. Our data show that CaM binds to the death domain of Fas (FasDD) with an apparent dissociation constant (Kd) of ~2 μM and 2:1 CaM:FasDD stoichiometry. The interactions between FasDD and CaM are endothermic and entropically driven, suggesting that hydrophobic contacts are critical for binding. We also show that both the N- and C-terminal lobes of CaM are important for binding. NMR and surface plasmon resonance data show that three CaM antagonists (N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide, tamoxifen, and trifluoperazine) greatly inhibit Fas-CaM interactions by blocking the Fas-binding site on CaM. Our findings provide the first structural evidence for Fas-CaM interactions and mechanism of inhibition and provide new insight into the molecular basis for a novel role of CaM in regulating Fas-mediated apoptosis.

Expression, Purification and Crystallization of the Xanthomonas euvesicatoria Dual Specificity Protein Tyrosine Phosphatase, AvrBs1.1

Phytopathogenic xanthomonads possess a type III secretion system that allows delivery of proteins, which serve to disrupt normal cellular function in the host. Avirulence proteins (Avr) are type III effector proteins that are recognized by specific R gene products in resistant hosts. A novel Avr protein, AvrBs1.1, from Xanthomonas euvesicatoria was recently found to elicit a delayed hypersensitive response on Capsicum annuum leaves. Amino acid sequence analysis of AvrBs1.1 has revealed the presence of a Dual‐Specificity Protein Tyrosine Phosphatase domain. Screening for novel resistance genes has identified a single binding partner of AvrBs1.1, the R gene product Bs7. Our laboratory has constructed homology models of AvrBs1.1 which have provided some insight into potential differences in activation of Bs7 in C. annuum, a better understanding of the activation mechanism will be gained by x‐ray crystallographic studies of the protein complexes. We have begun purifying recombinant AvrBs1.1 in quantities suitable for crystallization trials. The coding sequence of X. euvesicatoria AvrBs1.1 was cloned into pET21A, which was used to transform E. coli BL21 (DE3) cultures. The recombinant AvrBs1.1 was purified by a combination of metal chelating affinity and gel filtration chromatographic methods. Aliquots of pure protein were used to identify conditions suitable for growth of diffraction quality crystals.

Preparation of antibodies type IgY against Salmonella typhi lipopolysaccharide in chicken eggs

ipopolysaccharide was extracted from local isolate Sallmonella typhi (previously isolated and characterized) by hot EDTA method, and the extract was partially purified by gel filtration chromatography on sepharose Cl-6B gel. The results showed that the percentage of the carbohydrates amount in the partially purified LPS extract was 43.7%, while the percentage of binding proteins in the same extract was 0.7% with no nucleic acids was found. The molecular weight for the LPS was measured by the gel filtration chromatography method using Sepharose Cl-6B gel and was equivalent to 263000 Dalton. The LD¬50 of LPS was determined by injection of chicken embryos type Ice Brown in the charioallantoic membrane, and was 14.66 µg/Kg. In order to obtain anti S. typhi IgY antibodies, chickens were immunized with the partially purified S. typhi subcutaneously. The IgY antibodies were extracted from eggs yolk by water dilution method and the extract was partially purified by ammonium sulphate precipitation at ratio 60% saturation, and gel filtration chromatography on sepharose Cl-6B gel. The results showed that the protein amount was equivalent to 23.5 mg/ml; specific activity was 0.268, and an overall yield of 70%. The molecular weight for the IgY antibodies was measured by the gel filtration chromatography method using Sepharose Cl-6B gel and was found to be 178000 dalton. The concentration of anti S.typhi LPS IgY antibodies in chicken eggs were investigated by ELISA and was found to be 6.3 mg/ml, and there is a significant differences (P&lt;0.01).

Partial purification of acid phosphatase from human placenta by gel filtration chromatography method in sephadex G-150

Partial purification of acid phosphatase from human placenta by gel filtration chromatography method in sephadex G-150

원양산 오징어(Illex argentinus) 내장으로부터 Exopeptidase의 분획

원양산 오징어 내장 조효소로부터 아세톤법, 황산암모늄법, 음이온교환 크로마토그래피법 및 겔 여과법을 이용하여 exopeptidase를 분획한 다음, 각 분획방법별 fraction들의 효소 활성(총활성 및 비활성), 정제도 및 회수율 등을 검토하여 최적 분획조건을 구명하고자 하였다. 아세톤 분획법의 경우 아세톤의 최종농도가 30～40%가 되도록 분획하는 것이, 황산암모늄 분획법의 경우 황산암모늄을 60～70%의 포화농도가 되도록 분획하는 것이, 음이온교환 크로마토그래피의 경우 0.2 M NaCl을 이용하여 분획하는 것이, 그리고, 겔 여과의 경우 분자량 30～50 kDa 범위의 것을 분획하는 것이 효율적이었다. 분획방법별 최적 활성 fraction간의 상호비교에서 LeuPNA 및 ArgPNA에 대한 총활성 및 회수율은 겔여과가, 비활성 및 정제도는 황산암모늄에 의한 분획법이 가장 우수한 것으로 나타났다. 원양산 오징어 내장으로부터 탈 이온수로 조효소를 추출한 다음, 겔 여과로 분획한 exopeptidase의 식품가공소재로서 산업적 이용을 위해서는 겔여과법의 특성을 기초로 하여 추출 조효소로부터 연속 및 대량처리를 위한 공정개발이 필요할 것으로 사료된다.

Purification and Characterization of Peroxidase from Cauliflower (Brassica oleracea L. var. botrytis) Buds

Peroxidases (EC 1.11.1.7; donor: hydrogen peroxide oxidoreductase) are part of a large group of enzymes. In this study, peroxidase, a primer antioxidant enzyme, was purified with 19.3 fold and 0.2% efficiency from cauliflower (Brassica oleracea L.) by ammonium sulphate precipitation, dialysis, CM-Sephadex ion-exchange chromatography and Sephadex G-25 purification steps. The substrate specificity of peroxidase was investigated using 2,2'-azino-bis(3-ethylbenz-thiazoline-6-sulphonic acid) (ABTS), 2-methoxyphenol (guaiacol), 1,2-dihydroxybenzene (catechol), 1,2,3-trihyidroxybenzene (pyrogallol) and 4-methylcatechol. Also, optimum pH, optimum temperature, optimum ionic strength, stable pH, stable temperature, thermal inactivation conditions were determined for guaiacol/H(2)O(2), pyrogallol/H(2)O(2), ABTS/H(2)O(2), catechol/H(2)O(2) and 4-methyl catechol/H(2)O(2) substrate patterns. The molecular weight (M(w)) of this enzyme was found to be 44 kDa by gel filtration chromatography method. Native polyacrylamide gel electrophoresis (PAGE) was performed for isoenzyme determination and a single band was observed. K(m) and V(max) values were calculated from Lineweaver-Burk graph for each substrate patterns.

A high performance gel filtration chromatography method for γ-glutamyltransferase fraction analysis

The clinical relevance of serum γ-glutamyltransferase (GGT) activity, in areas other than hepatic function, has recently been increased by several epidemiological associations. Still, GGT remains a nonspecific test because of the influence of various pathophysiological factors. We devised a procedure based on gel filtration chromatography, followed by postcolumn injection of fluorescent GGT substrate (γ-glutamyl-7-amido-4-methylcoumarin), permitting the quantification of GGT fractions in serum or plasma. Plasma GGT molecular weight distribution was analyzed in healthy volunteers (20 males; mean ± SD age 38 ± 10 years; 20 females; age 44 ± 13; total GGT 21 ± 11 for males vs 13 ± 7 for females; P < 0.01). The method is highly sensitive (determination limit: 0.5 U GGT/L), with a linear dynamic range between 0.5 and 150 U/L for each fraction. Four GGT fractions of different molecular weight were detected in all subjects of both genders: b-GGT, m-GGT, s-GGT (likely lipoprotein-bound, molecular masses >2000, 940, and 140 kDa, respectively), and a free fraction (f-GGT, 70 kDa). f-GGT and s-GGT were the main fractions in subjects with lower and higher total GGT activity, respectively. Higher total GGT activity in males is related mainly to f-GGT ( P < 0.01). GGT fraction analysis may increase the sensitivity and specificity of the GGT activity test.

Fractionation of Zein by Size Exclusion Chromatography

Zein is a group of alcohol-soluble corn proteins, which consists of several individual proteins. A single-step gel filtration chromatography method was developed to fractionate individual zeins from ethanol extracts of whole corn. A Superdex prep 75 column was used with different mobile phases to fractionate the zeins, which were analyzed by SDS-PAGE and UV spectrophotometry. With 70% aqueous ethanol as the mobile phase, fractions containing a mixture of alpha-zein/beta-zein and alpha-zein/delta-zein were obtained. With ammonium bicarbonate added to the 70% ethanol mobile phase, it was possible to obtain beta-zein and delta-zein fractions devoid of other proteins. However, all fractions containing alpha-zein also contained minor amounts of delta-zein and/or beta-zein. Almost all fractions also contained non-protein impurities.

Cloning and characterization of three hypothetical secretion chaperone proteins from Xanthomonas axonopodis pv. citri

Xanthomonas axonopodis pv. citri (Xac) causes citrus canker in plantations around the world and is of particular significance in Brazil where its incidence has risen exponentially over the past decade. Approximately one third of the predicted Xac open reading frames show no homology, or homology with very low score with that of known sequences. It is believed that Xac utilizes secretion systems to transfer virulence proteins into susceptible eukaryotic cells. This process is assisted by secretion chaperones that maintain virulence proteins partly or completely unfolded during translocation. We have cloned three of these hypothetical secretion chaperones: XAC0419 and XAC1346 from type III secretion system (TTSS) and XACb0033 from type IV secretion system (TFSS). All proteins were cloned in a pET23a vector (Novagen), expressed at 37°C using a BL21(DE3)pLysS Escherichia coli strain and purified by ion exchange and gel-filtration chromatographic methods. Pure proteins were characterized using spectroscopic measurements: circular dichroism, and both static and lifetime emission fluorescence in the case of XACb0033. The analyzed proteins are stable at elevated temperatures (up to 65°C) and exhibit α-helix content from ∼30% (XACb003) to ∼87% (XAC1346). XACb0033 exhibits lifetimes in the fluorescence experiments that indicate different neighborhoods for its tryptophan residues. These chaperones have the characteristics of TTSS and TFSS: all are small, with a high α-helix content, and without ATP-binding or ATP-hydrolyzing activity.

Comparison of two gel filtration chromatographic methods for the purification of Lily symptomless virus

Lily symptomless virus (LSV) occurs frequently in many Lilium species worldwide and often causes developmental abnormalities such as a smaller flower and lower bulb yield. In this study, two moderate and efficient gel filtration chromatography (GFC) methods was compared, these two techniques were, respectively, based on Superdex-200 HR and Sephacryl S-1000 SF. The products purified by the two methods were then characterized by measurements with UV-spectrophotometer, reverse transcriptase (RT)-PCR, transmission electron microscope (TEM), polycrylamide gel electrophoresis (PAGE), Western blotting and matrix assisted laser desorption-ionisation/time-of-flight mass spectrometry (MALDI-TOF-MS). The final yield of purified LSV by the Superdex-200 HR GFC was 9.4 mg from 50 g of fresh infected tissues of Lanzhou lily. However, from the same amount tissues, only 5.6 mg of LSV were obtained by using Sephacryl S-1000 SF GFC. The Superdex-200 HR method was thus shown to be more suitable for the purification of LSV than the Sephacryl S-1000 SF GFC. The Superdex-200 HR method does not require costly equipment for density centrifugation and ultracentrifugation. Furthermore, it can provide an economical and efficient way to obtain purified products for the preparation of antibodies for serological diagnosis or LSV infection and related investigations.