Search

Small heat shock proteins (sHSPs) have been thought to function as chaperones, protecting their targets from denaturation and aggregation when organisms are subjected to various biotic and abiotic stresses. We previously reported an sHSP from Oryza sativa (OsHSP20) that homodimerizes and forms granules within the cytoplasm but its function was unclear. We now show that OsHSP20 transcripts were significantly up-regulated by heat shock and high salinity but not by drought. A recombinant protein was purified and shown to inhibit the thermal aggregation of the mitochondrial malate dehydrogenase (MDH) enzyme in vitro, and this molecular chaperone activity suggested that OsHSP20 might be involved in stress resistance. Heterologous expression of OsHSP20 in Escherichia coli or Pichia pastoris cells enhanced heat and salt stress tolerance when compared with the control cultures. Transgenic rice plants constitutively overexpressing OsHSP20 and exposed to heat and salt treatments had longer roots and higher germination rates than those of control plants. A series of assays using its truncated mutants showed that its N-terminal arm plus the ACD domain was crucial for its homodimerization, molecular chaperone activity in vitro, and stress tolerance in vivo. The results supported the viewpoint that OsHSP20 could confer heat and salt tolerance by its molecular chaperone activity in different organisms and also provided a more thorough characterization of HSP20-mediated stress tolerance in O. sativa.

A new organometallic nonlinear optical crystal triallylthiourea mercury bromide (ATMB) with space group R3c has been synthesized and grown by the temperature lowering method from aqueous solution. Its powder second harmonic generation (SHG) intensity is 2.5 times higher than that of urea. The crystal structure of ATMB is reported and also the relations between the crystal structure and nonlinear optical (NLO) effects are discussed.

Certain organic crystals have attracted much attention owing to their nonlinear optical coefficients, at least one to two orders of magnitude above those of inorganic nonlinear optical materials. However, none of them has so far actually been applied in frequency conversion devices used with high-, medium- or low-power lasers. In this article the authors discuss the major factors affecting frequency conversion efficiency and examine characteristics of some frequently mentioned organic crystals. The properties and structure characterization of a new type of nonlinear optical crystal are also reported and discussed.

Pot experiments were carried out to investigate the influence of different zinc (Zn) levels (0, 100, 200, 400 and 600 micromol x L(-1)) on the plant growth,activities of antioxidant enzymes, contents of chlorophyll a and b, accumulation and chemical forms of cadmium (Cd) in Capsicum annuum L. when exposed to Cd (20 mg x kg(-1)). The results showed that dry weights of leaf, stem, fruit and root, and contents of chlorophyll a and b in Capsicum annuum L. were increased by Zn (or = 400 micromol x L(-1)), while inhibited by high Zn (600 micromol x L(-1)). Activities of superoxide dismutase (SOD) and catalase (CAT) were reduced by Zn (or =400 micromol x L(-1)), the lowest activities of SOD and CAT were recorded in 400 micromol x L(-1) Zn, but activities of SOD and CAT were increased when Zn400 micromol x L(-1). Cadmium concentrations in stem, fruit and root of Capsicum annuum L. were decreased by 2.7%-5.4%, 7.5%-28.1% and 7.6%-21.8% in the presence of Zn when exposed to Cd. The total extractable Cd, NaCl- extractable Cd, water-extractable Cd and ethanol-extractable Cd in fruit were reduced by 7.7%-21.8%, 4.11%-23.6%, 54.5%-66.8% and 4.8%-86.7% in the presence of Zn,while acetic acid- extractable Cd and residual Cd were increased by 28.0%-68.0% and 12.6%-25.0%.

The data of the thermal expansion and specific heat of cadmium mercury thiocyanate crystal have been obtained. The specific heat is 0.7588 J/gC at room temperature. The thermal expansion occurs in the direction parallel to the c-axis, and the thermal contraction occurs in the direction parallel to the a-axis. The thermal expansion is the same as the thermal contraction at 353 K. The relationship between thermal properties and crystal structure is discussed.