The potent inhibitory activity of histone H1.2 C-terminal fragments on furin

Many physiologically important proproteins, pathogenic bacterial exotoxins and viral envelope glycoproteins are activated by the proprotein convertase furin, which makes furin inhibitor a hot target for basic research and drug design. Although synthetic and bioengineered inhibitors of furin have been well characterized, its endogenous inhibitor has not been directly purified from mammalian tissues to date. In this study, three inhibitors were purified from the porcine liver by using a combination of chromatographic techniques, and identified to be the C-terminal truncated fragments with different sizes of histone H1.2. The gene of porcine histone H1.2 was cloned and sequenced, further confirming the determined sequences. These three C-terminal fragments inhibited furin with Ki values around 2 x 10(-7) m while the full-length histone H1.2 inhibited it with a lesser activity, suggesting that the inhibitory activity relies on the C-terminal lysine-rich domain. Though the inhibition was temporary, these inhibitors were specific, and the reactive site of one C-terminal fragment was identified. A 36 amino acid peptide around the reactive site was synthesized, which could still inhibit furin with a Ki of 5.2 x 10(-7) m.     

Discriminative learning for protein conformation sampling

Protein structure prediction without using templates (i.e., ab initio folding) is one of the most challenging problems in structural biology. In particular, conformation sampling poses as a major bottleneck of ab initio folding. This article presents CRFSampler, an extensible protein conformation sampler, built on a probabilistic graphical model Conditional Random Fields (CRFs). Using a discriminative learning method, CRFSampler can automatically learn more than ten thousand parameters quantifying the relationship among primary sequence, secondary structure, and (pseudo) backbone angles. Using only compactness and self-avoiding constraints, CRFSampler can efficiently generate protein-like conformations from primary sequence and predicted secondary structure. CRFSampler is also very flexible in that a variety of model topologies and feature sets can be defined to model the sequence-structure relationship without worrying about parameter estimation. Our experimental results demonstrate that using a simple set of features, CRFSampler can generate decoys with much higher quality than the most recent HMM model.     

Redifferentiation of human hepatoma cells (SMMC-7721) induced by two new highly oxygenated bisabolane-type sesquiterpenes

Bisabolane-type sesquiterpenes are a class of biologically active compounds that has antitumour, antifungal, antibacterial, antioxidant and antivenom properties. We investigated the effect of two new highly oxygenated bisabolane-type sesquiterpenes (HOBS) isolated from Cremanthodium discoideum (C. discoideum) on tumour cells. Our results showed that HOBS induced morphological differentiation and reduced microvilli formation on the cell surface in SMMC-7721 cells. Flow cytometry analysis demonstrated that HOBS could induce cell-cycle arrest in the G1 phase. Moreover, HOBS was able to increase tyrosine-α-ketoglutarate transaminase activity, decrease α foetoprotein level and γ-glutamyl transferase activity. In addition, we found that HOBS inhibited the anchorageindependent growth of SMMC-7721 cells in a dose-dependent manner. Taken together, all the above observations indicate that HOBS might be able to normalize malignant SMMC-7721 cells by inhibiting cell proliferation and inducing redifferentiation.     

硫对大蒜生理生化指标及营养品质的影响

采用盆栽试验探讨了硫对大蒜生理生化指标及营养品质的影响．结果表明,土壤硫含量8．41mg·kg^-1时,大蒜叶片硝酸还原酶、POD活性、光合色素含量、光合速率、气孔导度和蒸腾速率较高;可溶性蛋白质含量及CAT活性却是以土壤硫含量为7．92mg·kg^-1时最高;SOD活性以较低土壤硫含量6．45mg·kg^-1时较高．同时,土壤硫含量为8．41mg·kg^-1时,鳞茎中大蒜素、可溶性糖和Vc及蒜薹中大蒜素、可溶性糖和可溶性蛋白质含量分别比对照增加33．67％、23．75％、68．82％、40．95％、3．45％和7．45％;较高土壤硫含量9．48mg·kg^-1有利于蒜薹中Vc和游离氨基酸及鳞茎中游离氨基酸和可溶性蛋白质含量的提高,分别比对照高出15．17％、20．93％、6．49％和8．07％．     

Multi-target-directed design,syntheses, and characterization of fluorescent bisphosphonate derivatives as multifunctional enzyme inhibitors in mevalonate pathway

Background

Mevalonate pathway is an important cellular metabolic pathway present in all higher eukaryotes and many bacteria. Four enzymes in mevalonate pathway, including MVK, PMK, MDD, and FPPS, play important regulatory roles in cholesterol biosynthesis and cell proliferation.

Methods

The following methods were used: cloning, expression and purification of enzymes in mevalonate pathway, organic syntheses of multifunctional enzyme inhibitors, measurement of their IC₅₀ values for above four enzymes, kinetic studies of enzyme inhibitions, molecular modeling studies, cell viability tests, and fluorescence microscopy.

Results and conclusions

We report our multi-target-directed design, syntheses, and characterization of two blue fluorescent bisphosphonate derivatives compounds 15 and 16 as multifunctional enzyme inhibitors in mevalonate pathway. These two compounds had good inhibition to all these four enzymes with their IC₅₀ values at nanomolar to micromolar range. Kinetic and molecular modeling studies showed that these two compounds could bind to the active sites of all these four enzymes. The fluorescence microscopy indicated that these two compounds could easily get into cancer cells.

General significance

Multifunctional enzyme inhibitors are generally more effective than single enzyme inhibitors, with fewer side effects. Our results showed that these multifunctional inhibitors could become lead compounds for further development for the treatment of soft-tissue tumors and hypercholesteremia.     

Label-free G-quadruplex-specific fluorescent probe for sensitive detection of copper(II) ion

An effective G-quadruplex-based probe has been constructed for rapid and sensitive detection of Cu(2+). In this probe, an anionic porphyrin, protoporphyrin IX (PPIX) served as a reference signal, which binds to G-quadruplex specifically and the fluorescence intensity increases sharply. While, in the presence of Cu(2+), the G-quadruplex can catalyze the related Cu(2+) insertion into the protoporphyrin, the fluorescent intensity is decreased. The fluorescence of the response ligand could be selectively quenched in the presence of Cu(2+) and not interfered by other metal ions. The probe provided an effective platform for reliable detection of Cu(2+) with a detection limit as low as 3.0nM, the high sensitivity was attributed to the strong metalation of PPIX with Cu(2+) catalyzed by G-quadruplex (PS5.M). Linear correlations were obtained over the logarithm of copper ion concentration in the range from 8×10(-9)M to 2×10(-6)M (R=0.998). The G-quadruplex-based probe also could be used to detect Cu(2+) in real water samples. Additionally, these striking properties endow the G-quadruplex-ligand with a great promise for analytical applications.     

Robust Prediction of t‐Year Survival with Data from Multiple Studies

Summary Recently meta‐analysis has been widely utilized to combine information across multiple studies to evaluate a common effect. Integrating data from similar studies is particularly useful in genomic studies where the individual study sample sizes are not large relative to the number of parameters of interest. In this article, we are interested in developing robust prognostic rules for the prediction of t ‐year survival based on multiple studies. We propose to construct a composite score for prediction by fitting a stratified semiparametric transformation model that allows the studies to have related but not identical outcomes. To evaluate the accuracy of the resulting score, we provide point and interval estimators for the commonly used accuracy measures including the time‐specific receiver operating characteristic curves, and positive and negative predictive values. We apply the proposed procedures to develop prognostic rules for the 5‐year survival of breast cancer patients based on five breast cancer genomic studies.     

Nitrogen cycling in forest soils across climate gradients in Eastern China

A ¹⁵N tracing study was carried out to investigate the potential gross nitrogen (N) dynamics in thirteen forest soils in Eastern China ranging from temperate to tropical zones (five coniferous forests, six deciduous broad-leaf forests, one temperate mixed forest, one evergreen broad-leaf forests ecosystems), and to identify the major controlling factors on N cycling in these forest ecosystems. The soil pH ranged from 4.3 to 7.9 and soil organic carbon (SOC) ranged from 6.6 g?kg^?1 to 83.0 g?kg^?1. The potential gross N transformation rates were quantified by ¹⁵N tracing studies where either the ammonium or nitrate pools were ¹⁵N labeled in parallel treatments. Gross mineralization rates ranged from 0.915 μg N g^?1 soil day^?1 to 2.718 μg N g^?1 soil day^?1 in the studied forest soils. The average contribution of labile organic-N (M _Nlab ) to total gross mineralization (M _Nrec +M _Nlab ) was 86% (58% to 99%), indicating that turnover of labile organic N plays a dominant role in the studied forest ecosystems. The gross mineralization rates in coniferous forest soils were significantly lower (ranging between 0.915 and 1.228 μg N g^?1 soil day^?1) compared to broad-leaf forest soils (ranging from 1.621 to 2.718 μg N g^?1 soil day^?1) (p?<?0.01). Thus, the dominant vegetation may play an important role in regulating soil N mineralization. Nitrate production (nitrification) occurred via two pathways, oxidation of NH ₄ ⁺ and organic N the forest soils. Correlations with soil pH indicated that this is a key factor controlling the oxidation of NH ₄ ⁺ and organic N in theses forest ecosystems. NH ₄ ⁺ oxidation decreased with a decline in pH while organic N oxidation increased. The climatic conditions (e.g. moisture status) at the various sites governed the NO ₃ ^? -N consumption processes (dissimilatory NO ₃ ^? reduction to NH ₄ ⁺ (DNRA) or immobilization of NO ₃ ^? ). Total NO ₃ ^? consumption and the proportion of total NO ₃ ^? consumption to total NO ₃ ^? production decreased with an increase in the drought index of ecosystems, showing that strong interactions appear to exist between climatic condition (e.g. the drought index), N mineralization and the rate of DNRA. Interactions between vegetation, climatic conditions govern internal N cycling in these forests soils.