A ratiometric fluorescence sensor for tetracycline detection based on two fluorophores derived from Partridge tea.

Blue fluorescent carbon dots (PCDs) were prepared by hydrothermal method with Partridge tea. The ethanol extract of Partridge tea (PEE) was found to emit red fluorescence. Thus, a novel ratiometric sensor was constructed by simply mixing the two fluorophores derived from Partridge tea. The presence of tetracycline (TET) at lower concentrations enhanced the emission peak at 508 nm of PCDs and had a negligible effect on the emission peak at 680 nm of PEE. TET at higher concentrations led to  quenching  both the fluorescence of PCDs and PEE via inner filter effect and fluorescence resonance energy transfer, separately. Good linearities for the detection of TET were obtained in the ranges 0.67 to 15.00 µM and 33.33 to 266.67 µM, with limit of detection of 0.095 µM. The sensor was successfully applied to detect TET in lake water and milk samples with good recoveries ranging from 93.27 ± 4.04% to 107.30 ± 6.16%. This study provided a simple, selective, sensitive, rapid, and environmentally friendly method of monitoring TET residues in the environment and food.

Networking activities and perceptions of HIV risk among male migrant market vendors in China.

HIV research among internal migrants in China has not fully explored the contexts and perceptions of "risk". In 2011, urban markets in Liuzhou, China were mapped, and sixty male vendors, age 22-56, were selected for in-depth interviews on migration, social and family life, and perceptions and practices of sexual risk behavior. Participants were evenly divided among higher income shop and small stall vendors. All men were sexually active. Only the shop vendors reported non-marital sexual partners, including concurrent partners (n = 15), commercial partners (n = 10), and other sexual relationships (n = 11). Shop vendors engaged in networking activities that facilitated commercial and non-commercial high-risk sex. Perceptions of HIV risk from commercial sex led some men to doubt the protective ability of condoms and rely on local (unproven) self-protection techniques. Networking activities played a role in high-risk sex and shaping migrants' risk perceptions and health practices. The networks created through these processes could also be used to facilitate health promotion activities.

Affected by HIV stigma: interpreting results from a population survey of an urban center in Guangxi, China.

We aimed to identify factors related to HIV stigma in Liuzhou, Guangxi province, a city in southwest China with high HIV prevalence. We used a multi-stage cluster randomized sample of the general population to survey 852 adults. We conducted ordinal logistic regression analyses to test factors associated with punishment and isolation stigma. Eighteen percent of respondents agreed that people with HIV should be punished, and 40% agreed that people living with HIV (PLHIV) should be isolated. Punishment stigma was associated with age, having three or more sexual partners, and TV watching. Isolation stigma was associated with age, urban residence and a history of STI. HIV transmission knowledge was low, and having correct knowledge attenuated the association with punishment and isolation stigma. Despite programs in China to provide care and treatment for PLHIV, HIV stigma is common in this region. Targeted interventions need to focus on fears related to HIV and PLHIV.

Coping strategies for HIV-related stigma in Liuzhou, China.

This study explores the feelings, experiences, and coping strategies of people living with HIV (PLHIV) in Liuzhou, China. In a southwestern Chinese city with high HIV prevalence, we conducted semi-structured in-depth interviews with 47 PLHIV selected to represent individuals who had acquired HIV via different acquisition routes. Many participants felt severely stigmatized; they commonly reported having very low self-esteem and feelings of despair. Based on style of coping and whether it occurred at the interpersonal or intrapersonal level, four types of coping that participants used to deal with HIV-associated stigma were identified: (1) Compassion (Passive/Avoidant-Interpersonal); (2) Hiding HIV status (Passive/Avoidant-Intrapersonal); (3) Social support (Active/Problem-focused-Interpersonal; and (4) Self-care (Active/Problem-focused-Intrapersonal). Educational and stigma-reduction interventions targeting potential social support networks for PLHIV (e.g., family, close friends, and peers) could strengthen active interpersonal PLHIV coping strategies. Interventions teaching self-care to PLHIV would encourage active intrapersonal coping, both of which may enhance PLHIV quality of life in Liuzhou, China.

Novel ß-cyclodextrin doped carbon dots for host-guest recognition-assisted sensing of isoniazid and cell imaging.

In the present study, novel ß-cyclodextrin doped carbon dots (CCDs) were prepared via a simple one-pot hydrothermal method at a mild temperature (140 °C), using mixtures of ß-cyclodextrin and citric acid as precursors. By characterizing the chemical properties of CCDs prepared at 140 °C and 180 °C, the importance of low-temperature reaction for preservation of the specific structure of ß-CD was elucidated. The CCDs showed excellent optical properties and were stable to changes in pH, ionic strength and light irradiation. Since the fluorescence of the CCDs could be selectively quenched by isoniazid (INZ) through specific host-guest recognition effects, a convenient isoniazid fluorescence sensor was developed. Under the optimal conditions, the sensor exhibited a relatively low detection limit of 0.140 µg mL-1 and a wide detection range from 0.2 µg mL-1 to 50 µg mL-1 for INZ detection. Furthermore, the sensor was employed successfully for the determination of INZ in urine samples with satisfactory recovery (91.1-109.5%), displaying potential in clinical applications. Finally, low cytotoxicity of the prepared CCDs was confirmed using the CCK-8 method, followed by application in HepG2 cell imaging.

[Study on the seasonal variations of the active components in Acer truncatum leaves and the inhibitory ability on fatty acid synthase].

OBJECTIVE: To study the dynamic variations of the contents of total polyphenols, flvonoids and chlorogenic acid from Acer truncatum leaves in different months, and their inhibitory activities on fatty acid synthase. METHODS: Spectrophotometry was used to determine the contents of total polyphenols, flavonoids and chlorogenic acid in extracts and the extracts' inhibitory effects were also investigated. RESULTS: All Leaves picked from May to November have inhibitory effect. But the contents of polyphenols in leaves of July appeared to be higher than other months', and consequently exhibited stronger inhibition against FAS. CONCLUSION: A positive correlation between the content of polyphenols in leaves extract and the inhibitory efficacy on FAS could be established.

[Synthesis and preliminary evaluation of antidiabetic activity of 4-(3-(4-bromophenyl)-3-oxo-1-arylpropylamino)-N-(5-methylisoxazol-3-yl)benzenesulfonamide].

Diabetes mellitus is a common metabolic disease with a high and growing prevalence affecting 4% of the population worldwide, the development of safe and effective therapeutic drug is the major thrust for chemists and pharmacists. To search for active antidiabetic lead compound, we designed and synthesized some novel beta-amino ketone derivatives containing sulfamethoxazole moiety directly through Mannich reaction of sulfamethoxazole, 4-bromoacetophenone and some aromatic aldehydes catalyzed by concentrated hydogen chloride or iodine in the solution of ethanol at 24-40 degrees C with convenient operation, mild reaction condition and satisfactory yield (32%-90%). Their chemical structures were characterized by 1H NMR, 13C NMR, MS and HR-MS. Biological activity tests showed that, in the range of low concentration (5-10 microg x mL(-1)), these title compounds to a certain degree possess protein tyrosine phosphatase 1B (PTP1B) inhibitory activity and a-glucosidase inhibitory activity, moreover, some could activate peroxisome proliferator-activated receptor response element (PPRE) moderately. The PPRE agonist activities of seven compounds are almost 40% of that of Pioglitazone (the positive control), compound 12 shows the strongest activity (66.35%) among them. Thus, it was found that some of 4-(3-(4-bromophenyl)-3-oxo-1-arylpropylamino)-N-(5-methyl-isoxazol-3-yl) benzenesulfonamide containing sulfamethoxazole moiety exhibited antidiabetic activity for the first time.

[Study on extraction of polyphenols from the leaves of Acer truncatum and their inhibitory abilities on fatty acid synthase].

OBJECTIVE: To optimize a technical process for extracting the polyphenols that can inhibit fatty acid synthase by ethanol from the leaves of Acer truncatum. METHODS: The extracting time, extracting temperature, extracting solvent and the ratio of solvent to raw material were studied by L16 (4(5)) orthogonal experiments. The extraction rate of polyphenols and the inhibitory efficiency on the fatty acid synthase were utilized as evaluating criteria, and the optimum conditions for the extraction were obtained through summing up the above factors. RESULTS: The efficient technological conditions were as follows: the concentration of ethanol was 60% (v/v), the ratio of solvent to raw material was 1 g: 30 mL; and the stirring time was 1.5 h at 50 degrees C. CONCLUSION: The polyphenols that extracted from the leaves of Acer truncatum have inhibitory activity against fatty acid synthase and some of them have stronger inhibitory effect.

The antibacterial efficacy of an aceraceous plant [Shantung maple (Acer truncatum Bunge)] may be related to inhibition of bacterial beta-oxoacyl-acyl carrier protein reductase (FabG).

Polyphenols, including flavonoids, are the major components of the extracts from aceraceous plants. They possess remarkable antibacterial and antitumour activity. Our study focused on whether the inhibition of the bacterial type II fatty acid synthesis system is the mechanism for the antibacterial effect of the related plant polyphenols. Extracts obtained from the fallen leaves of the Shantung maple (Acer truncatum Bunge) using different solvents, and the related pure compound PGG (1,2,3,4,6-penta-O-galloyl-beta-D-glucose), potently inhibited the FabG (beta-oxoacyl-ACP reductase) steps in the fatty-acid-elongation cycle with the IC(50) values between 0.9 and 7.2 microg/ml. An ethyl acetate extract appeared to inhibit FabG reductase in a mixed manner with NADPH, as did PGG with NADPH, demonstrating that they interfered with the binding of the cofactor to the enzyme. Gram-positive and Gram-negative bacteria and some fungi were used to evaluate the antibacterial abilities of different extract samples. The experiments showed that a higher polyphenol content of the extracts led to a more potent inhibitory capacity against FabG, thus enhancing the antibacterial efficacy.

The isolation of 1,2,3,4,6-penta-O-galloyl-beta-D-glucose from Acer truncatum Bunge by high-speed counter-current chromatography.

High-speed counter-current chromatography (HSCCC) was successfully used for the isolation and purification of 1,2,3,4,6-penta-O-galloyl-beta-D-glucose from the ethyl acetate extract of the leaves of Acer truncatum Bunge using a two-phase system composed of n-hexane-ethyl acetate-methanol-water at a volume ratio of (0.25:5:1:5, v/v/v/v) for the first time. Each injection of 80 mg crude extract yielded 7.25 mg of pure 1,2,3,4,6-penta-O-galloyl-beta-D-glucose. High-performance liquid chromatography (HPLC) analyses of the CCC fraction revealed that the purity of 1,2,3,4,6-penta-O-galloyl-beta-D- glucose was over 95%.

Effect of heat and pH denaturation on the structure and conformation of recombinant human hepatic stimulator substance.

Hepatic stimulator substance (HSS) is a novel liver-specific growth-promoting factor. Although HSS has been successfully crystallized, several properties of this protein have yet to be determined. This study shows that recombinant human HSS (rhHSS) is a dimer with a molecular mass of 31 kDa, the protein is weakly acidic and has an isoelectric point (pI) of 4.50. RhHSS was able to protect hepatoma cells from H2O2-induced apoptosis and to stimulate cell growth. The recombinant protein was thermostable up to 80 degrees C and resistant to changes in pH, as determined by synchronous fluorescence and far-UV circular dichroism (CD). Within the range of pH 4.0-10.0, rhHSS assumed a folded conformation identical to the secondary structure of the original, native protein and a native-like far-UV CD spectrum. Denatured rhHSS could be partly reconstituted with respect to its structure, but not its activity. Thus, rhHSS is a structurally stable protein insensitive to thermal and acid-alkaline denaturation.

Apoptotic activity of frog Bombina maxima skin albumin.

Albumin, the most abundant protein components of blood plasma, is synthesized and secreted by liver cells in vertebrates. Recently, it was demonstrated that frog Bombina maxima albumin is also expressed in skin. Both B. maxima albumins from skin and serum (BmA-skin and BmA-serum) have similar biochemical characteristics except that the former contains haem b. Present studies showed that BmA-skin exhibited cytotoxic activity on H9 and C8166 cells. Pretreated with hemin to induce erythroid differentiation, K562 cells lost their resistance to cytotoxicity of BmA-skin. After treating cells with BmA-skin for 48 h, 50 percentage cytotoxic concentrations (CC(50)) of BmA-skin on H9, C8166 and hemin-treated K562 cells were 1.31+/-0.09, 1.59+/-0.08 and 2.28+/-0.06 microM, respectively. The cell death induced by BmA-skin was mediated by apoptosis of the tested cell lines, as demonstrated by nuclear morphological changes, DNA fragmentation and DNA hypodiploidy of apoptosis cells. At BmA-skin concentration of 2 microM, 27.3%, 19.7% and 17.8% of H9, C8166 and hemin-treated K562 cells were found to be apoptotic. In contrast, BmA-serum possessed no cytotoxic and apoptosis-inducing activity on all the cell lines tested, even with concentration used up to 15 microM. These results indicated that bound haem b in BmA-skin contributed significantly to its cytotoxic and apoptosis-inducing activity on the cell lines assayed.

[The study on the technique of sexing bovine pre-implantation embryos with two-temperature gradient multiplex PCR].

For the stable, reliable, fast method of sexing bovine pre-implantation embryos is still play very important role in husbandry production, the amplification experiment under the condition of the two-temperature gradient PCR was done with bovine samples such as genome, cloning embryos, embryos respectively. As a result, the stable, simple, fast method of two-temperature gradient PCR for sexing bovine pre-implantation embryos was obtained, which only took 57 minutes to identify the embryo sex. A total of 30 dairy embryos were sexed with the two-temperature gradient PCR method in the study. 15 identified embryos (11 female, 4 male) were transferred into 15 recipient cows, among them 7 were pregnant after 60 days. In the end, 5 female calves were aborted in late pregnancy, and 1 female and 1 male dairy calf were born. The sexes of aborted and born calves were fully in accordance with the embryo sex predetermination with PCR method.

Frog albumin is expressed in skin and characterized as a novel potent trypsin inhibitor.

A novel potent trypsin inhibitor was purified and characterized from frog Bombina maxima skin. A full-length cDNA encoding the protein was obtained from a cDNA library constructed from the skin. Sequence analysis established that the protein actually comprises three conserved albumin domains. B.maxima serum albumin was subsequently purified, and its coding cDNA was further obtained by PCR-based cloning from the frog liver. Only two amino acid variations were found in the albumin sequences from the skin and the serum. However, the skin protein is distinct from the serum protein by binding of a haem b (0.95 mol/mol protein). Different from bovine serum albumin, B. maxima albumin potently inhibited trypsin. It bound tightly with trypsin in a 1:1 molar ratio. The equilibrium dissociation constants (KD) obtained for the skin and the serum proteins were 1.92 x 10(-9) M and 1.55 x 10(-9) M, respectively. B. maxima albumin formed a noncovalent complex with trypsin through an exposed loop formed by a disulfide bond (Cys53-Cys62), which comprises the scissile bond Arg58(P1)-His59(P1'). No inhibitory effects on thrombin, chymotrypsin, elastase, and subtilisin were observed under the assay conditions. Immunohistochemical study showed that B. maxima albumin is widely distributed around the membranes of epithelial layer cells and within the stratum spongiosum of dermis in the skin, suggesting that it plays important roles in skin physiological functions, such as water economy, metabolite exchange, and osmoregulation.

Maximin 9, a novel free thiol containing antimicrobial peptide with antimycoplasma activity from frog Bombina maxima.

Amphibian skin is a rich resource of antimicrobial peptides, like maximins and maximin Hs from frog Bombina maxima. Novel cDNA clones encoding a precursor protein, which comprises a novel maximin peptide (maximin 9) and reported maximin H3, were isolated from two constructed skin cDNA libraries of B. maxima. The predicted primary structure of maximin 9 is GIGRKFLGGVKTTFRCGVKDFASKHLY-NH2. A surprising substitution is at position 16, with a free cysteine in maximin 9 rather than usual conserved glycine in other reported maximins. Maximin 9, the homodimer form and its Cys16 to Gly16 mutant were synthesized and their antimicrobial activities were evaluated. Unlike previously reported maximin 3, the tested bacterial and fungal strains were resistant to maximin 9, its homodimer and the Cys16 to Gly16 mutant (with MICs>100 microM). On the other hand, interestingly, while eight clinical Mollicutes strains were generally resistant to maximin 9 homodimer and its Cys16 to Gly16 mutant, most of them are sensitive to maximin 9 at a peptide concentration of 30 microM, especially in the presence of dithiothreitol. These results indicate that the presence of a reactive Cys residue in maximin 9 is important for its antimycoplasma activity. The diversity of antimicrobial peptide cDNA structures encountered in B. maxima skin cDNA libraries and the antimicrobial specificity differences of the peptides may reflect well the species' adaptation to the unique microbial environments.

Cloning of novel bombesin precursor cDNAs from skin of Bombina maxima.

Amphibian skin is a rich resource of bioactive peptides like proline-rich bombesin from frog Bombina maxima. A novel cDNA clone encoding a precursor protein that comprises proline-rich bombesin and a novel peptide, designated as bombestatin, was isolated from a skin cDNA library of B. maxima. The predicted primary structure of the novel peptide is WEVLLNVALIRLELLSCRSSKDQDQKESCGMHSW, in which two cysteines form a disulfide bond. A BLAST search of databases did not detect sequences with significant similarity. Bombestatin possesses dose-dependent contractile activity on rat stomach strips. The differences between cDNAs encoding PR-bombesin plus bombestatin and PR-bombesin alone are due to fragment insertions located in 3'-coding region and 3'-untranslational region, respectively.

Effects of magnesium ions on thermal inactivation of alkaline phosphatase.

The effect of Mg2+ on the thermal inactivation and unfolding of calf intestinal alkaline phosphatase has been studied at different temperatures and Mg2+ concentrations. Increasing the Mg2+ concentration in the denatured system significantly enhanced the inactivation and unfolding of the enzyme during thermal inactivation. The analysis of the kinetic course of substrate reaction during thermal inactivation showed that at 47 degrees C the increased free Mg2+ concentration caused the inactivation rate to increase. Increasing the temperature strengthened the effect of Mg2+ on the thermal inactivation. Control experiment showed that this is not due to salt effect. The time course of fluorescence emission spectra showed that the emission maximum for Mg2+-containing system was always higher than that of Mg2+-free system, and the higher temperature enhanced this difference. In addition, Mg2+ also enhanced the unfolding rate of the enzyme at 47 degrees C. The potential biological significance of these results are discussed.

Refolding and reactivation of calf intestinal alkaline phosphatase with excess magnesium ions.

It is well known that Mg(2+) is an essential component in many biological processes. This research investigated the courses of both the reactivation and the refolding in the absence and presence of Mg(2+) ions. Calf intestinal alkaline phosphatase (CIP) was extensively denatured in 3 M guanidine hydrochloride (GdnHCl) solution for 2 h. Under suitable renaturation conditions, about 60-70% of the activity was recovered in the absence and presence of different magnesium ion concentrations. The refolding processes followed two-phase courses, whereas the reactivation processes were monophasic after dilution in proper solutions with or without Mg(2+). The magnesium ions affected both the reactivation and the refolding courses of unfolded CIP. A comparison of rate constants for the refolding of unfolded CIP with those for recovery of enzyme activity at different Mg(2+) concentrations showed that they were not synchronized. The activity recovery was speeded up due to the presence of Mg(2+) ions; while the refolding course of unfolded CIP was somewhat inhibited by the excess Mg(2+).

Weight-reducing effect of Acer truncatum Bunge may be related to the inhibition of fatty acid synthase.

In order to study the anti-obesity ability and inhibition towards fatty acid synthase (FAS) of the extract, a 70% ethanol extract of Acer truncatum Bunge (AT) leaves was further extracted with ethyl acetate. FAS is a very significant lipogenic enzyme, participating in energy metabolism in vivo; it has also been observed that FAS inhibitors might be potent anti-obesity agents. Experimental results on animals showed that the extract significantly reduced food intake and adipose, and effectively controlled weight evolution. Lipogenesis inhibition might be regarded as one of the reasons for the weight control and adipose reduction by AT. The extract was further isolated using a series of column chromatography that yielded 10 known compounds. 1,2,3,4,6-Penta-O-galloyl-ß-D-glucose was found to be one of the major active constituents in the extract of AT.

Purification and characterization of albumin from frog skin of Duttaphrynus melanostictus.

Following determination of trypsin inhibitory activity, a serine protease inhibitor was purified and characterized from frog Duttaphrynus melanostictus serum. It was identified as serum albumin, with molecular weight of 67 kDa (DmA-serum). Different from bovine serum albumin, DmA-serum potently inhibited trypsin with similar K(i) values around 1.6 × 10⁻7 M. No inhibitory effect on thrombin, chymotrypsin, elastase and subtilisin was observed under the assay conditions. The N-terminal amino acid is EAEPHSRI. Subsequently, a protein with same N-terminal amino acid was purified from skin, termed as DmA-skin. However, DmA-skin is distinct from DmA-serum by binding of a haem b (0.5 mol/mol protein), and with low trypsin inhibitory activity. Frog albumin is distributed in frog skin and exhibited trypsin inhibitory activity, suggesting that it plays important roles in skin physiological functions, like water economy, metabolite exchange and osmoregulation, etc.