Unfolding energetics and conformational stability of DLC8 monomer

To understand the rules governing the protein folding process it is essential to study the stability and unfolding of small monomeric proteins. Here, I present the pH dependent thermal unfolding energetics and conformational stability analysis of monomeric Dynein light chain protein (DLC8) in the pH range 3.5-2.0. DLC8 is the smallest and the most conserved light chain among the light chains of the dynein motor assembly. Thermal unfolding of DLC8 monomer is much complex with the presence of transient intermediates, which is in contrast to the notion that small proteins unfold via simple two-state process. The unfolding seems to be more cooperative at lower pH and the temperature of highest conformational stability (T(s)) is found to be maximum (295.7 K) at pH 2.76. Stability curves have been simulated to understand the thermodynamic parameters that govern the shapes of the experimentally obtained curves. Further, an effort has been made to correlate the observed differences in the denaturation energetics with the protein sequence in order to throw light on the structure-folding paradigm of the DLC8 monomer.     

A chemically induced new pea (Pisum sativum) mutant SGECdt with increased tolerance to, and accumulation of, cadmium

BACKGROUND AND AIMS: To date, there are no crop mutants described in the literature that display both Cd accumulation and tolerance. In the present study a unique pea (Pisum sativum) mutant SGECd(t) with increased Cd tolerance and accumulation was isolated and characterized. METHODS: Ethylmethane sulfonate mutagenesis of the pea line SGE was used to obtain the mutant. Screening for Cd-tolerant seedlings in the M2 generation was performed using hydroponics in the presence of 6 microm CdCl2. Hybridological analysis was used to identify the inheritance of the mutant phenotype. Several physiological and biochemical characteristics of SGECd(t) were studied in hydroponic experiments in the presence of 3 microm CdCl2, and elemental analysis was conducted. KEY RESULTS: The mutant SGECd(t) was characterized as having a monogenic inheritance and a recessive phenotype. It showed increased Cd concentrations in roots and shoots but no obvious morphological defects, demonstrating its capability to cope well with increased Cd levels in its tissues. The enhanced Cd accumulation in the mutant was accompanied by maintenance of homeostasis of shoot Ca, Mg, Zn and Mn contents, and root Ca and Mg contents. Through the application of La(+3) and the exclusion of Ca from the nutrient solution, maintenance of nutrient homeostasis in Cd-stressed SGECd(t) was shown to contribute to the increased Cd tolerance. Control plants of the mutant (i.e. no Cd treatment) had elevated concentrations of glutathione (GSH) in the roots. Through measurements of chitinase and guaiacol-dependent peroxidase activities, as well as proline and non-protein thiol (NPT) levels, it was shown that there were lower levels of Cd stress both in roots and shoots of SGECd(t). Accumulation of phytochelatins [(PCcalculated) = (NPT)-(GSH)] could be excluded as a cause of the increased Cd tolerance in the mutant. CONCLUSIONS: The SGECd(t) mutant represents a novel and unique model to study adaptation of plants to toxic heavy metal concentrations.     

Immunomodulation of activated hepatic stellate cells by mesenchymal stem cells

Bone marrow-derived mesenchymal stem cells (MSCs) have been reported to prevent the development of liver fibrosis in a number of pre-clinical studies. Marked changes in liver histopathology and serological markers of liver function have been observed without a clear understanding of the therapeutic mechanism by which stem cells act. We sought to determine if MSCs could modulate the activity of resident liver cells, specifically hepatic stellate cells (SCs) by paracrine mechanisms using indirect cocultures. Indirect coculture of MSCs and activated SCs led to a significant decrease in collagen deposition and proliferation, while inducing apoptosis of activated SCs. The molecular mechanisms underlying the modulation of SC activity by MSCs were examined. IL-6 secretion from activated SCs induced IL-10 secretion from MSCs, suggesting a dynamic response of MSCs to the SCs in the microenvironment. Blockade of MSC-derived IL-10 and TNF-alpha abolished the inhibitory effects of MSCs on SC proliferation and collagen synthesis. In addition, release of HGF by MSCs was responsible for the marked induction of apoptosis in SCs as determined by antibody-neutralization studies. These findings demonstrate that MSCs can modulate the function of activated SCs via paracrine mechanisms provide a plausible explanation for the protective role of MSCs in liver inflammation and fibrosis, which may also be relevant to other models of tissue fibrosis.     

Reduced expression of INK4a/ARF genes in stem-like sphere cells from rat sarcomas

The presence of cancer stem cells, in both hematopoietic and solid malignancies, has been recently linked to their pathogenesis. We aimed to identify the characteristics and stem-like properties of sphere-colony forming cells in rat osteosarcoma and malignant fibrous histiocytoma cell lines. The results showed that both cell lines possessed an ability to form spherical, clonally expanding colonies in anchorage-independent, serum-starved conditions in N2/1% methylcellulose medium. The sphere cells showed stem-like properties with the ability to self-renew, and expressed the stem cell-related STAT3 and Bmi1 genes. Interestingly, spheres from both sarcomas remarkably decreased the expression of INK4a/ARF locus genes, p16(INK4a) and p19(ARF), which could be related to the resistance against cell senescence and apoptosis. Spheres showed strong tumorigenicity with metastatic potential in vivo via the inoculation into syngeneic rats, suggesting the presence of these populations might contribute to the tumor development such as metastasis via the resistance to apoptotic stimuli.     

Heat shock augments myosin phosphatase target-subunit phosphorylation

Our previous study demonstrated that heat shock augmented vascular contraction. In the present study, we hypothesized that heat shock augments myosin phosphatase target-subunit (MYPT1) phosphorylation resulting in augmented vascular contraction. Endothelium-denuded rat aortic rings were mounted in organ baths, exposed to heat shock (42 degrees C for 45 min), and subjected to contraction 4 h after the heat shock followed by Western blot analysis for MLC(20) (the 20 kDa light chains of myosin II) or MYPT1. The contractile responses in both control and heat shock-treated aorta were inhibited by Y27632, an inhibitor of Rho-kinase. The level of the MLC(20) and MYPT1(Thr855) phosphorylation in response to KCl was higher in heat shock-treated aorta than that in timed-control. The increased MYPT1(Thr855) phosphorylation was inhibited by Y27632 (1.0 microM) in parallel with inhibition of MLC(20) phosphorylation and vascular contraction. These results indicate that heat shock augments MYPT1 phosphorylation resulting in augmented vascular contraction.     

Homochiral metal-organic coordination networks from l-typtophan

Three homochiral metal-organic coordination networks [Co₂(l-Trp)₂(Py)₆] · Py · (ClO₄)₂ (1), [Ni(l-Trp)(Py)₃] · H₂O · ClO₄ (2) and [Co₂(l-Trp)(INT)₂(H₂O)₂(ClO₄)] (3), all containing natural amino acid l-HTrp (l-typtophan), were hydrothermally synthesized and structurally characterized. The compounds 1 and 2 crystallize in the orthorhombic space group C222₁, with a = 10.731(2) Å, b = 19.709(4) Å, c = 27.365(6) Å and Z = 4 for 1 and a = 10.710(10) Å, b = 20.088(18) Å, c = 27.63(3) Å and Z = 8 for 2, respectively. The compound 3 has the monoclinic space group P2₁, with a = 8.1934(14) Å, b = 13.209(2) Å, c = 12.464(2) Å, β = 104.107(3)° and Z = 2. Both 1 and 2 consist of 1D helical chains. Compound 3 is composed of 2D networks, which further assemble into a 3D supramolecular structure via weak interlayer interactions. The optically pure amino acid l-HTrp plays an important role leading to homochiral structures reported here.     

[Tm(hfac)3(NITPhOPh)]∞: A new member of a lanthanide-based Single Chain Magnets family

The polymeric coordination compound of formula [Tm(hfac)₃(NITPhOPh)]_∞ (where NITPhOPh is a nitronyl-nitroxide radical) has been synthesized and found to belong to the only reported family of isostructural Single Chain Magnets. Both static and dynamic magnetic measurements have been performed, and a dependence of the out-of-phase signal on the frequency is observed below 3 K. Scaling procedures indicate Ising magnetic anisotropy. Comparison of the extracted parameters with those of the previously reported isostructural compounds confirms a trend along the lanthanide series.     

生物沥滤污泥土地利用适用性分析

研究了污泥生物沥滤对重金属(Cu、Pb和Zn)形态、营养物质和SO42-存在形式的影响,分析生物沥滤污泥土地利用的适用性。结果表明:生物沥滤后,污泥上清液中重金属通过固液分离而去除,污泥中Cu、Pb和Zn的去除率分别为84.1%、34.8%和80.0%,残存于污泥中的重金属含量大幅降低,且生物有效性低,提高了污泥土地利用的安全性。污泥经生物沥滤后氮、磷和钾的流失分别为38.2%、52.1%和42.8%,但仍能保持较好的肥效。采用X-射线衍射光谱分析发现,残留于污泥中的SO24-主要与Ca2 相结合,较为稳定,生物沥滤后的污泥施用于土地后对环境影响较小。     

具年龄结构的种群在破碎化生境中的空间分布模型

随着人类和其他生物赖以生存的环境破碎化程度的加剧,许多以前是连续分布的物种,目前不得不在破碎化生境(斑块)中求生存,所以,种群在破碎化生境(斑块)中分布问题的研究对生物保护和生境重建意义重大．本文运用Leslie矩阵和Markov链建立了一个具年龄结构的种群在破碎化生境中随时间动态变化的分布模型,讨论了种群在该生境中持续存在以及灭绝的条件．