Functional conservation of GENOMES UNCOUPLED1 in plastid-to-nucleus retrograde signaling in tomato

Retrograde signaling between plastids and the nucleus is vital for chloroplast biogenesis and environmental responses. GENOMES UNCOUPLED1 (GUN1) was proposed to be a central integrator of multiple retrograde signaling pathways in the model plant Arabidopsis thaliana (Arabidopsis). However, the function of GUN1 orthologs in other plant species has not been well studied. Here, we found that many GUN1 orthologs from the Solanaceae family have a short N-terminus before the first pentatricopeptide repeat (PPR) motif which is predicted as intrinsically disordered regions (IDRs). Functional analyses of tomato (Solanum lycopersicum L.) GUN1 (SlGUN1), which does not contain N-terminal IDRs, show that it can complement the GUN phenotype of the Arabidopsis gun1 mutant (Atgun1). However, in contrast to the AtGUN1 protein, which does contain the N-terminal IDRs, the SlGUN1 protein is highly accumulated even after chloroplast biogenesis is completed, suggesting that the N-terminal IDRs may determine the stability of the GUN1 protein. Furthermore, we generated tomato Slgun1 genome-edited mutants via the CRISPR-Cas9 system. The Slgun1 mutants exhibited a typical GUN phenotype under lincomycin (Lin) or norflurazon (NF) treatment. Moreover, Slgun1 mutants are hypersensitive to low concentrations of Lin or NF. Taken together, our results suggest that, although lacking the N-terminal IDRs, SlGUN1 plays conserved roles in plastid retrograde signaling in tomato plants.

[Research on the framework of biosafety standards for pathogenic microbial laboratories]

Developing and implementing biosafety standards for pathogenic microbiology laboratories is essential to achieving scientific, efficient, and standardized management and operation. This article analyzes the current standardization construction in biosafety in pathogenic microbiology laboratories domestically and internationally. It proposes a framework for the biosafety standard system of pathogenic microbiology laboratories, which mainly includes four parts: basic standards, management standards, technical standards, and industry applications. It provides a reference for the standardization work of pathogenic microbiology laboratories and helps to standardize the biosafety industry in China.

Chloroplast proteostasis: A story of birth, life, and death

Protein homeostasis (proteostasis) is a dynamic balance of protein synthesis and degradation. Because of the endosymbiotic origin of chloroplasts and the massive transfer of their genetic information to the nucleus of the host cell, many protein complexes in the chloroplasts are constituted from subunits encoded by both genomes. Hence, the proper function of chloroplasts relies on the coordinated expression of chloroplast- and nucleus-encoded genes. The biogenesis and maintenance of chloroplast proteostasis are dependent on synthesis of chloroplast-encoded proteins, import of nucleus-encoded chloroplast proteins from the cytosol, and clearance of damaged or otherwise undesired "old" proteins. This review focuses on the regulation of chloroplast proteostasis, its interaction with proteostasis of the cytosol, and its retrograde control over nuclear gene expression. We also discuss significant issues and perspectives for future studies and potential applications for improving the photosynthetic performance and stress tolerance of crops.

GUN control in retrograde signaling: How GENOMES UNCOUPLED proteins adjust nuclear gene expression to plastid biogenesis

Communication between cellular compartments is vital for development and environmental adaptation. Signals emanating from organelles, so-called retrograde signals, coordinate nuclear gene expression with the developmental stage and/or the functional status of the organelle. Plastids (best known in their green photosynthesizing differentiated form, the chloroplasts) are the primary energy-producing compartment of plant cells, and the site for the biosynthesis of many metabolites, including fatty acids, amino acids, nucleotides, isoprenoids, tetrapyrroles, vitamins, and phytohormone precursors. Signals derived from plastids regulate the accumulation of a large set of nucleus-encoded proteins, many of which localize to plastids. A set of mutants defective in retrograde signaling (genomes uncoupled, or gun) was isolated over 25 years ago. While most GUN genes act in tetrapyrrole biosynthesis, resolving the molecular function of GUN1, the proposed integrator of multiple retrograde signals, has turned out to be particularly challenging. Based on its amino acid sequence, GUN1 was initially predicted to be a plastid-localized nucleic acid-binding protein. Only recently, mechanistic information on the function of GUN1 has been obtained, pointing to a role in plastid protein homeostasis. This review article summarizes our current understanding of GUN-related retrograde signaling and provides a critical appraisal of the various proposed roles for GUNs and their respective pathways.

[Analysis of pregnancy outcome after fertility-preserving treatment among women with atypical endometrial hyperplasia or endometrial carcinoma]

Objective: To analyze the pregnancy outcome, influencing factors and recurrence of fertility-preserving therapy for women with atypical endometrial hyperplasia (AEH) or endometrial carcinoma (EC). Methods: The multi-center retrospective study included 107 women with AEH or EC for fertility-preserving therapy in 10 hospitals from January 1st, 2009 to December 31st, 2018. The clinical pregnancy rate, live birth rate and recurrence of 66 patients with urgent child-bearing requirements after fertility-preserving treatment were analyzed. Results: (1) Among the 66 AEH and EC women with urgent child bearing requirements, 24 women chose spontaneous pregnancy, the clinical pregnancy rate was 54.2% (13/24) and the live birth rate was 41.7% (10/24), the median time from fertility-preserving therapy withdrawal to clinical pregnancy was 5.5 months. Forty-two women chose assisted reproductive technology (ART), the clinical pregnancy rate was 59.5% (25/42) and the live birth rate was 35.7% (15/42), the median time from fertility-preserving therapy withdrawal to clinical pregnancy was 19.5 months. The time from fertility-preserving therapy withdrawal to pregnancy in women receiving ART was significantly longer than that in women with spontaneous pregnancy (P=0.048). (2) Age and intrauterine adhesions were independent factors affecting the clinical pregnancy rate (P<0.05). (3) Among 107 patients with AEH or EC, the recurrence rate was 27.1% (29/107). Among the 42 cases who chose ART, 9 of them recurred before ART treatment, who received the fertility-preserving therapy again and then ART treatment, 8 women got clinical pregnancy,5 of them delivered at least a live birth. Conclusions: Women with AEH or EC could achieved satisfactory clinical pregnancy rate and live birth rate after fertility-preserving therapy. Age and intrauterine adhesions are independent factors affecting clinical pregnancy rate. The women with recurrent AEH or EC could be treated with fertility-preserving therapy again and get a satisfactory pregnancy outcome.

Extensive Posttranscriptional Regulation of Nuclear Gene Expression by Plastid Retrograde Signals

Retrograde signals emanate from the DNA-containing cell organelles (plastids and mitochondria) and control the expression of a large number of nuclear genes in response to environmental and developmental cues. Previous studies on retrograde signaling have mainly analyzed the regulation of nuclear gene expression at the transcript level. To determine the contribution of translational and posttranslational regulation to plastid retrograde signaling, we combined label-free proteomics with transcriptomic analysis of Arabidopsis (Arabidopsis thaliana) seedlings and studied their response to interference with the plastid gene expression pathway of retrograde signaling. By comparing the proteomes of the genomes uncoupled1 (gun1) and gun5 mutants with the wild type, we show that GUN1 is critical in the maintenance of plastid protein homeostasis (proteostasis) when plastid translation is blocked. Combining transcriptomic and proteomic analyses of the wild type and gun1, we identified 181 highly translationally or posttranslationally regulated (HiToP) genes. We demonstrate that HiToP photosynthesis-associated nuclear genes (PhANGs) are largely regulated by translational repression, while HiToP ribosomal protein genes are regulated posttranslationally, likely at the level of protein stability without the involvement of GUN1. Our findings suggest distinct posttranscriptional control mechanisms of nuclear gene expression in response to plastid-derived retrograde signals. They also reveal a role for GUN1 in the translational regulation of several PhANGs and highlight extensive posttranslational regulation that does not necessitate GUN1. This study advances our understanding of the molecular mechanisms underlying intracellular communication and provides new insight into cellular responses to impaired plastid protein biosynthesis.

Control of retrograde signalling by protein import and cytosolic folding stress

Communication between organelles and the nucleus is essential for fitness and survival. Retrograde signals are cues emitted from the organelles to regulate nuclear gene expression. GENOMES UNCOUPLED1 (GUN1), a protein of unknown function, has emerged as a central integrator, participating in multiple retrograde signalling pathways that collectively regulate the nuclear transcriptome. Here, we show that GUN1 regulates chloroplast protein import through interaction with the import-related chaperone cpHSC70-1. We demonstrated that overaccumulation of unimported precursor proteins (preproteins) in the cytosol causes a GUN phenotype in the wild-type background and enhances the GUN phenotype of the gun1 mutant. Furthermore, we identified the cytosolic HSP90 chaperone complex, induced by overaccumulated preproteins, as a central regulator of photosynthetic gene expression that determines the expression of the GUN phenotype. Taken together, our results suggest a model in which protein import capacity, folding stress and the cytosolic HSP90 complex control retrograde communication.

High-level expression of the HIV entry inhibitor griffithsin from the plastid genome and retention of biological activity in dried tobacco leaves

KEY MESSAGE

The potent anti-HIV microbicide griffithsin was expressed to high levels in tobacco chloroplasts, enabling efficient purification from both fresh and dried biomass, thus providing storable material for inexpensive production and scale-up on demand. The global HIV epidemic continues to grow, with 1.8 million new infections occurring per year. In the absence of a cure and an AIDS vaccine, there is a pressing need to prevent new infections in order to curb the disease. Topical microbicides that block viral entry into human cells can potentially prevent HIV infection. The antiviral lectin griffithsin has been identified as a highly potent inhibitor of HIV entry into human cells. Here we have explored the possibility to use transplastomic plants as an inexpensive production platform for griffithsin. We show that griffithsin accumulates in stably transformed tobacco chloroplasts to up to 5% of the total soluble protein of the plant. Griffithsin can be easily purified from leaf material and shows similarly high virus neutralization activity as griffithsin protein recombinantly expressed in bacteria. We also show that dried tobacco provides a storable source material for griffithsin purification, thus enabling quick scale-up of production on demand.

Control of Retrograde Signaling by Rapid Turnover of GENOMES UNCOUPLED1

The exchange of signals between cellular compartments coordinates development and differentiation, modulates metabolic pathways, and triggers responses to environmental conditions. The proposed central regulator of plastid-to-nucleus retrograde signaling, GENOMES UNCOUPLED1 (GUN1), is present at very low levels, which has hampered the discovery of its precise molecular function. Here, we show that the Arabidopsis (Arabidopsis thaliana) GUN1 protein accumulates to detectable levels only at very early stages of leaf development, where it functions in the regulation of chloroplast biogenesis. GUN1 mRNA is present at high levels in all tissues, but GUN1 protein undergoes rapid degradation (with an estimated half-life of ∼4 h) in all tissues where chloroplast biogenesis has been completed. The rapid turnover of GUN1 is controlled mainly by the chaperone ClpC1, suggesting degradation of GUN1 by the Clp protease. Degradation of GUN1 slows under stress conditions that alter retrograde signaling, thus ensuring that the plant has sufficient GUN1 protein. We also find that the pentatricopeptide repeat motifs of GUN1 are important determinants of GUN1 stability. Moreover, overexpression of GUN1 causes an early flowering phenotype, suggesting a function of GUN1 in developmental phase transitions beyond chloroplast biogenesis. Taken together, our results provide new insight into the regulation of GUN1 by proteolytic degradation, uncover its function in early chloroplast biogenesis, and suggest a role in developmental phase transitions.

Selective deletion of Pten in theca-interstitial cells leads to androgen excess and ovarian dysfunction in mice

Theca cell-selective Pten mutation (tPtenMT) in mice resulted in increases in PDK1 and Akt phosphorylation, indicating an over-activation of PI3K signaling in the ovaries. These mice displayed elevated androgen levels, ovary enlargement, antral follicle accumulation, early fertility loss and increased expression of Lhcgr and genes that are crucial to androgenesis. These abnormalities were partially reversed by treatments of PI3K or Akt inhibitor. LH actions in Pten deficient theca cells were potentiated. The phosphorylation of Foxo1 was increased, while the binding of Foxo1 to forkhead response elements in the Lhcgr promoter was reduced in tPtenMT theca cells, implying a mechanism by which PI3K/Akt-induced upregulation of Lhcgr in theca cells might be mediated by reducing the inhibitory effect of Foxo1 on the Lhcgr promoter. The phenotype of tPtenMT females is reminiscent of human PCOS and suggests that dysregulated PI3K cascade in theca cells may be involved in certain types of PCOS pathogenesis.

Controlling multiple filaments by relativistic optical vortex beams in plasmas

Filamentation dynamics of relativistic optical vortex beams (OVBs) propagating in underdense plasma is investigated. It is shown that OVBs with finite orbital angular momentum (OAM) exhibit much more robust propagation behavior than the standard Gaussian beam. In fact, the growth rate of the azimuthal modulational instability decreases rapidly with increase of the OVB topological charge. Thus, relativistic OVBs can maintain their profiles for significantly longer distances in an underdense plasma before filamentation occurs. It is also found that an OVB would then break up into regular filament patterns due to conservation of the OAM, in contrast to a Gaussian laser beam, which in general experiences random filamentation.

Practices and thinking of laboratory detection in the aid to West Africa to fight against Ebola

BACKGROUND

The outbreak of Ebola virus disease in West Africa has brought great disaster to the people's health in affected countries. China dispatched first group of public health experts and medical staff to Sierra Leone in September 2014 to fight Ebola.

METHODS

To systematically collect huge amount of primary data, and to make analysis, draw conclusions and lessons in terms of six aspects, respectively as training before departure, local disease information, track of epidemic situation, transformation of temporary laboratory, detection of Ebola virus samples as well as assessment through single blind test.

RESULTS

1) Our team has launched preparatory works in advance before going to Sierra Leone. 2) Malaria is the country's severest infectious disease. 3) Observation centers were overcrowded with large number of suspected cases being inspected, implying high risk of nosocomial infection. 4) A BSL-II laboratory with 3 work areas and 2 buffer areas was built, achieving several major functions within 6 days. 5) Confirmed by South African Raqqa laboratory, our detection accuracy reached 100%. 6) At one week before return, the daily average sample amount of our team reached 66 cases and our detection capability was equivalent to that of USA.

CONCLUSIONS

Successful experience from fighting against Ebola in Sierra Leone could be summarized as: 1) Optimized processes and scientific security measures are prerequisite to improving the detection ability. 2) The close collaboration between laboratory and observation center has created a new model of China's foreign aid. 3) Comprehensive information investigation and training lay a solid foundation for the successful completion of tasks.

Molecular dynamics simulation of the interfacial structure of [C(n)mim][PF6] adsorbed on a graphite surface: effects of temperature and alkyl chain length

The structures and diffusion behaviors of a series of ionic liquids [C(n)mim][PF(6)] (n = 1, 4, 8 and 12) on a graphite surface have been investigated by means of molecular dynamics simulation. It was found that three or four ordering layers of ionic liquids were formed near the graphite surface, and this layering structure was stable over the temperature range investigated. At the liquid/vacuum interface, the ionic liquid with a butyl chain had a monolayer ordering surface, while [C(8)mim][PF(6)] and [C(12)mim][PF(6)] exhibited a bilayer ordering with a polar domain sandwiched between two orientational nonpolar domains. More impressively, the simulated results showed that for the ionic liquids with alkyl chains longer than C(4), the adjacent alkyl chains in the whole film tended to be parallel to each other, with the imidazolium rings packed closely together. This indicated that the ionic liquids have a better regulated short-range structure than was previously expected. It was also found that both in the bottom layer and in the bulk region, the diffusion of the alkyl chains was much faster than that of the polar groups. However, as the alkyl chain length increased, the charge delocalization in the cation and the enhanced van der Waals interaction between the nonpolar groups contributed by reducing this difference in the diffusivity of major groups.

A rare case of the coexistence of ovarian clear cell carcinoma, mucinous cystadenoma, and endometriosis in the same ovary

Clear cell carcinomas and endometrioid carcinomas are associated with endometriosis. The association of clear cell carcinomas with mucinous lesions has only been reported infrequently, and with mucinous cystadenoma has been rarely reported. This is the second reported case of the coexistence of ovarian clear cell carcinoma, mucinous cystadenoma, and endometriosis in the same ovary. A 57-year-old woman presented with lower abdominal pain for three weeks. Ultrasonography revealed a 16 x 14 x 10 cm mass in the left ovary with solid and cystic components. Hysterectomy and bilateral salpingo-oophorectomy were performed. Histopathological examination of the left ovary revealed the presence of clear cell carcinoma, mucinous cystadenoma, and endometriosis. Continuity between the areas of mucinous epithelium and clear cell carcinoma were noted; this may suggest that clear cell carcinoma may arise from endometriosis or mucinous cystic tumors.

Arabidopsis β-ketoacyl-[acyl carrier protein] synthase i is crucial for fatty acid synthesis and plays a role in chloroplast division and embryo development

Lipid metabolism plays a pivotal role in cell structure and in multiple plant developmental processes. β-Ketoacyl-[acyl carrier protein] synthase I (KASI) catalyzes the elongation of de novo fatty acid (FA) synthesis. Here, we report the functional characterization of KASI in the regulation of chloroplast division and embryo development. Phenotypic observation of an Arabidopsis thaliana T-DNA insertion mutant, kasI, revealed multiple morphological defects, including chlorotic (in netted patches) and curly leaves, reduced fertility, and semidwarfism. There are only one to five enlarged chloroplasts in the mesophyll cells of chlorotic sectors of young kasI rosette leaves, indicating suppressed chloroplast division under KASI deficiency. KASI deficiency results in a significant change in the polar lipid composition, which causes the suppressed expression of FtsZ and Min system genes, disordered Z-ring placement in the oversized chloroplast, and inhibited polymerization of FtsZ protein at mid-site of the chloroplast in kasI. In addition, KASI deficiency results in disrupted embryo development before the globular stage and dramatically reduces FA levels (~33.6% of the wild type) in seeds. These results demonstrate that de novo FA synthesis is crucial and has pleiotropic effects on plant growth. The polar lipid supply is important for chloroplast division and development, revealing a key function of FA synthesis in plastid development.

Global analysis of gene expression profiles in Brassica napus developing seeds reveals a conserved lipid metabolism regulation with Arabidopsis thaliana

In order to study Brassica napus fatty acid (FA) metabolism and relevant regulatory networks, a systematic identification of fatty acid (FA) biosynthesis-related genes was conducted. Following gene identification, gene expression profiles during B. napus seed development and FA metabolism were performed by cDNA chip hybridization (>8000 EST clones from seed). The results showed that FA biosynthesis and regulation, and carbon flux, were conserved between B. napus and Arabidopsis. However, a more critical role of starch metabolism was detected for B. napus seed FA metabolism and storage-component accumulation when compared with Arabidopsis. In addition, a crucial stage for the transition of seed-to-sink tissue was 17-21 d after flowering (DAF), whereas FA biosynthesis-related genes were highly expressed primarily at 21 DAF. Hormone (auxin and jasmonate) signaling is found to be important for FA metabolism. This study helps to reveal the global regulatory network of FA metabolism in developing B. napus seeds.

A genome-wide scan reveals candidate susceptibility loci for pig hernias in an intercross between White Duroc and Erhualian

Pig scrotal/inguinal and umbilical hernias are the most prevalent congenital disorders in pigs and often cause animal welfare problems and economic loss. To identify susceptibility loci for these traits, a genome-wide scan with 194 microsatellite markers covering the pig genome was performed in a White Duroc x Erhualian resource population with 23 scrotal/inguinal F(2) animals, 50 umbilical F(2) animals, and their unaffected siblings. A sex-average linkage map with a total length of 2,350.3 cM and an average marker interval of 12.84 cM was constructed. Both nonparametric genome-wide linkage (NPL) analysis and transmission disequilibrium test (TDT) were implemented to detect closely linked markers. The NPL analysis revealed 11 chromosomal regions on SSC1, 2, 3, 6, 7, 8, 10, and 11 for umbilical hernia and 5 regions on SSC2, 4, 8, 13, and 16 for scrotal/inguinal hernia, whereas the TDT test identified susceptibility loci for umbilical hernia on SSC1, 2, 4, 7, 10, 13, 14, and 15 and for scrotal/inguinal hernias on SSC2, 8, 10, and 18. The most promising loci were SWR1928 on SSC7 and SW830 on SSC10 for umbilical hernia, and SW933 on SSC8 for scrotal hernia, which were consistently detected by both NPL and TDT. Several previously reported chromosomal regions for scrotal/inguinal hernia were confirmed, and new evidence for linkage with this pig defect was found. Moreover, susceptibility loci for pig umbilical hernia were detected for the first time.

Shanghai RAPESEED Database: a resource for functional genomics studies of seed development and fatty acid metabolism of Brassica

The Shanghai RAPESEED Database (RAPESEED, http://rapeseed.plantsignal.cn/) was created to provide the solid platform for functional genomics studies of oilseed crops with the emphasis on seed development and fatty acid metabolism. The RAPESEED includes the resource of 8462 unique ESTs, of which 3526 clones are with full length cDNA; the expression profiles of 8095 genes and the Serial Analysis of Gene Expression (SAGE, 23,895 unique tags) and tag-to-gene data during seed development. In addition, a total of approximately 14,700 M3 mutant populations were generated by ethylmethanesulfonate (EMS) mutagenesis and related seed quality information was determined using the Foss NIR System. Further, the TILLING (Targeting Induced Local Lesions IN Genomes) platform was established based on the generated EMS mutant population. The relevant information was collected in RAPESEED database, which can be searched through keywords, nucleotide or protein sequences, or seed quality parameters, and downloaded.

Structure-based discovery of small molecule inhibitors targeted to protein tyrosine phosphatase 1B

Protein tyrosine phosphatases (PTPases) are involved in the control of tyrosine phosphorylation levels in the cell and are believed to be crucial for the regulation of a multitude of cellular functions. A detailed understanding of the role played by PTPases in various signaling pathways has not yet been achieved, and potent and selective PTPase inhibitors are essential in the quest to determine the functionality of individual PTPases. Using the DOCK methodology, we have carried out a structure-based, computer-assisted search of an available chemical database in order to identify low molecular weight, nonpeptidic PTP1B inhibitors. We have identified several organic molecules that not only possess inhibitory activity against PTP1B but which also display significant selectivity for PTP1B. This indicates that although structural features important for pTyr recognition are conserved among different PTPases, it is possible to generate selective inhibitors targeted primarily to the catalytic site. Kinetic analysis and molecular modeling experiments suggest that the PTP1B active site possesses significant plasticity such that substituted and extended aromatic systems can be accommodated. The newly identified molecules provide a molecular framework upon which therapeutically useful compounds can ultimately be based, and systematic optimization of these lead compounds is likely to further enhance their potency and selectivity.

[Diphasic regulatory effect of lishen injection on sex hormones in senile female patients with coronary heart disease of kidney deficiency type]

Effects of Lishen injection on serum estradiol (E2), testosterone (T) and the E2/T ratio in 30 cases of postmenopausal patients with coronary heart disease and of Kidney Deficiency type were observed. Results showed that: (1) Serum E2 and the E2/T ratio were lower (P < 0.01) in the group of Kidney-Yin Deficiency type and higher (P < 0.01) in the group of Kidney-Yang Deficiency type as compared with normal control. (2) After treatment with Lishen injection the levels of serum E2 and the E2/T ratio were elevated in the former (P < 0.01) and lowered in the later (P < 0.01). Both were approaching to normal level (P > 0.05). (3) The levels of T in both groups were unaffected (P > 0.05) before and after treatment. These results suggested the imbalance of Kidney-Yin and Kidney-Yang is related to the disturbance of sex hormones and Lishen injection could not only regulate the Kidney-Yin and Kidney-Yang, improve the symptoms of Kidney Deficiency, but also could convert the abnormal change of sex hormone, it has a good diphasic regulatory effect on E2, and is beneficial on balance of sex hormones of both sex in the inner environment of human body.

Myoglobin-NO at low pH: free four-coordinated heme in the protein pocket

In either sperm whale or horse heart myoglobin, binding of NO and lowering of solution pH work together to weaken, and ultimately break, the bond between iron and the proximal histidine. This is reminiscent of the reaction observed at neutral pH in the case of guanylate cyclase, the heme enzyme that catalyzes the conversion of GTP to cGMP. Bond breaking is characterized by a spectral change from a nine-line to a three-line ESR signal and accompanied by a shift from 420 to 387 nm in the UV-vis spectrum of the Soret band maximum. Analysis of the pH-dependent spectral changes shows that they are reversible, at least within a few hours, that the transition is cooperative, involving six protons during pH lowering but only two as it is raised, and that the pK is about 4.7. Different proteins exhibit different pK values, which are generally lower than that for "chelated" protoheme. The pK differences reflect the extra bond stability afforded by the protein structure. Investigations of thermal and photochemical NO displacement by CO suggest that the local pocket around the ligand, although significantly altered (according to circular dichroism investigations), nonetheless still imposes a barrier against the outward diffusion of ligand into the solvent. Nanosecond and picosecond flash photolysis shows that in proteins at low pH there is an extremely efficient geminate recombination of the ligand with the four-coordinated species through a single-exponential process. This occurs to a significantly larger extent than for the case of NO-"chelated" protoheme (where no distal barrier for ligand is present). At neutral pH, when the proximal histidine bond is intact, the geminate recombination for NO takes longer and displays multiexponential kinetics. Altogether, these results suggest that, even though distal effects probably also play a role, proximal effects make an important contribution in modulating ligand-iron bond formation.

Comparative study on antigenicity and immunogenicity of 26-28 kDa antigen and recombinant Sj26 (RSj26) of Schistosoma japonicum

This paper reports a comparison of the recombinant Sj26 (rSj26) antigen derived from the Philippine strain and the 26-28 kDa antigen isolated and purified from the Chinese strain of Schistosoma japonicum with respect to their antigenicity and immunogenicity. The results showed that there were obvious cross reactions between rSj26 and 26-28 kDa antigen when rSj26 antigen was tested against specific antibodies in sera of mice infected with the Chinese strain of S. japonicum or the 26-28 kDa antigen was tested against specific anti-rSj26 antibodies by ELISA, IFA and Western blotting. Both the 26-28 kDa and the rSj26 antigen had weak cross reactions with SEA antigen. The worm reduction rate after challenging with Chinese strain cercariae in mice immunized with rSj26 was 26-32%, similar to that in mice immunized with 26-28 kDa antigen. It is suggested that rSj26 antigen can induce a certain level of specific protective immunity in the host against infection by the Chinese strain of S. japonicum cercariae.