Low pressure reversibly driving colossal barocaloric effect in two-dimensional vdW alkylammonium halides.

Plastic crystals as barocaloric materials exhibit the large entropy change rivalling freon, however, the limited pressure-sensitivity and large hysteresis of phase transition hinder the colossal barocaloric effect accomplished reversibly at low pressure. Here we report reversible colossal barocaloric effect at low pressure in two-dimensional van-der-Waals alkylammonium halides. Via introducing long carbon chains in ammonium halide plastic crystals, two-dimensional structure forms in (CH3-(CH2)n-1)2NH2X (X: halogen element) with weak interlayer van-der-Waals force, which dictates interlayer expansion as large as 13% and consequently volume change as much as 12% during phase transition. Such anisotropic expansion provides sufficient space for carbon chains to undergo dramatic conformation disordering, which induces colossal entropy change with large pressure-sensitivity and small hysteresis. The record reversible colossal barocaloric effect with entropy change ΔSr ~ 400 J kg-1 K-1 at 0.08 GPa and adiabatic temperature change ΔTr ~ 11 K at 0.1 GPa highlights the design of novel barocaloric materials by engineering the dimensionality of plastic crystals.

Molecular Characterization of a Novel N-Acetylneuraminate Lyase from a Deep-Sea Symbiotic Mycoplasma.

N-acetylneuraminic acid (Neu5Ac) based novel pharmaceutical agents and diagnostic reagents are highly required in medical fields. However, N-acetylneuraminate lyase（NAL）for Neu5Ac synthesis is not applicable for industry due to its low catalytic efficiency. In this study, we biochemically characterized a deep-sea NAL enzyme (abbreviated form: MyNal) from a symbiotic Mycoplasma inhabiting the stomach of a deep-sea isopod, Bathynomus jamesi. Enzyme kinetic studies of MyNal showed that it exhibited a very low Km for both cleavage and synthesis activities compared to previously described NALs. Though it favors the cleavage process, MyNal out-competes the known NALs with respect to the efficiency of Neu5Ac synthesis and exhibits the highest kcat/Km values. High expression levels of recombinant MyNal could be achieved (9.56 mol L-1 culture) with a stable activity in a wide pH (5.0-9.0) and temperature (40-60 °C) range. All these features indicated that the deep-sea NAL has potential in the industrial production of Neu5Ac. Furthermore, we found that the amino acid 189 of MyNal (equivalent to Phe190 in Escherichia coli NAL), located in the sugar-binding domain, GX189DE, was also involved in conferring its enzymatic features. Therefore, the results of this study improved our understanding of the NALs from different environments and provided a model for protein engineering of NAL for biosynthesis of Neu5Ac.

Influence of Water in the Photogeneration and Properties of a Bifunctional Quinone Methide.

Quinone methides (QM) are crucial reactive species in molecular biology and organic chemistry, with little known regarding the mechanism(s) for the generation of short-lived reactive QM intermediates from relevant precursors in aqueous solutions. In this study, several time-resolved spectroscopy methods were used to directly examine the photophysics and photochemical pathways of 1,1'-(2,2'-dihydroxy-1,1'-binaphthyl-6,6'-diyl)bis(N,N,N-trimethylmethanaminium) bromide (BQMP-b) from initial photoexcitation to the generation of the key reactive binol QM intermediate (BQM) in aqueous solution. The fluorescence of BQMP-b is effectively quenched with a small amount of water, which suggests an excited state intramolecular proton transfer (ESIPT) occurs. The kinetics isotope effects observed in femtosecond and nanosecond time-resolved transient absorption experiments provide evidence for the participation of water molecules in the BQMP-b singlet excited state ESIPT process and in the subsequent -HNMe3+ group release and ground state intramolecular proton transfer that give rise to production of the reactive BQM intermediate. Nanosecond time-resolved resonance Raman (ns-TR3) measurements were also employed to investigate the structure and properties of several intermediates, including the key reactive BQM in aqueous solution. The ns-TR3 and density functional theory (DFT) computational results were compared, and this indicates the binol moiety and water molecules both have important roles in the characteristics and structure of the key reactive BQM intermediate produced from BQMP-b. The results presented here also provide new benchmark characterization of bifunctional quinone methide intermediates that can be utilized to guide direct time-resolved spectroscopic study of the alkylation and interstrand cross-linking reactions of quinone methides with DNA in the future.

Line shape analysis of two-dimensional infrared spectra.

Ultrafast two-dimensional infrared (2D IR) spectroscopy probes femtosecond to picosecond time scale dynamics ranging from solvation to protein motions. The frequency-frequency correlation function (FFCF) is the quantitative measure of the spectral diffusion that reports those dynamics and, within certain approximations, can be extracted directly from 2D IR line shapes. A variety of methods have been developed to extract the FFCF from 2D IR spectra, which, in principle, should give the same FFCF parameters, but the complexity of real experimental systems will affect the results of these analyses differently. Here, we compare five common analysis methods using both simulated and experimental 2D IR spectra to understand the effects of apodization, anharmonicity, phasing errors, and finite signal-to-noise ratios on the results of each of these analyses. Our results show that although all of the methods can, in principle, yield the FFCF under idealized circumstances, under more realistic experimental conditions they behave quite differently, and we find that the centerline slope analysis yields the best compromise between the effects we test and is most robust to the distortions that they cause.

Effect of Chinese traditional healthcare exercises on 136 junior school students.

OBJECTIVE: To observe the physiological and psychological effects of Chinese traditional healthcare exercises (CTHE) on the adolescents. METHODS: A total of 136 healthy students of junior school were recruited and randomly divided into the test group (68 cases) and the control group (68 cases). The subjects in the test group practiced CTHE, while those in the control group did "the 8th radio calisthenics", an official recommended calisthenics for promoting healthcare in China, 3 times a week, and 7 weeks practicing overall. The general body function examination and the meridian energy detection system were used to determine the effects of the two groups. RESULTS: (1) After exercise, the chest circumference and heart rate were increased significantly (P<0.01), and both the systolic pressure (SP) and diastolic pressure (DP) were decreased significantly (P<0.01), while the weight had no significant change (P>0.05) in the test group. In the control group, the chest circumference, the SP and DP had no significant improvement (P>0.05), while the heart rate was significantly increased and the weight was significantly decreased (P<0.01). (2) The test group achieved significant positive changes in the performance status, state of mind and fatigue index (P<0.01 or P<0.05), while the control group only achieved a significant positive change in performance status (P<0.01), and a negative significant decrease in the autonomic nerve function (P<0.05). CONCLUSION: Junior school students would get physiological and psychological benefit from practicing CTHE, and which is suitable for them to practice.

2D IR spectroscopy using four-wave mixing, pulse shaping, and IR upconversion: a quantitative comparison.

Recent technological advances have led to major changes in the apparatuses used to collect 2D IR spectra. Pulse shaping offers several advantages including rapid data collection, inherent phase stability, and phase-cycling capabilities. Visible array detection via upconversion allows the use of visible detectors that are cheaper, faster, more sensitive, and less noisy than IR detectors. However, despite these advantages, many researchers are reluctant to implement these technologies. Here we present a quantitative study of the S/N of 2D IR spectra collected with a traditional four-wave mixing (FWM) apparatus, with a pulse shaping apparatus, and with visible detection via upconversion to address the question of whether weak chromophores at low concentrations are still accessible with such an apparatus. We find that the enhanced averaging capability of the pulse shaping apparatus enables the detection of small signals that would be challenging to measure even with the traditional FWM apparatus, and we demonstrate this ability on a sample of cyanylated dihydrofolate reductase.

3-picolyl azide adenine dinucleotide as a probe of femtosecond to picosecond enzyme dynamics.

Functionally relevant femtosecond to picosecond dynamics in enzyme active sites can be difficult to measure because of a lack of spectroscopic probes that can be located in the active site without altering the behavior of the enzyme. We have developed a new NAD(+) analog 3-Picolyl Azide Adenine Dinucleotide (PAAD(+)), which has the potential to be a general spectroscopic probe for NAD-dependent enzymes. This analog is stable and binds in the active site of a typical NAD-dependent enzyme formate dehydrogenase (FDH) with characteristics similar to those of natural NAD(+). It has an isolated infrared transition with high molar absorptivity that makes it suitable for observing enzyme dynamics using 2D IR spectroscopy. 2D IR experiments show that in aqueous solution, the analog undergoes complete spectral diffusion within hundreds of femtoseconds consistent with the water hydrogen bonding dynamics that would be expected. When bound to FDH in a binary complex, it shows picosecond fluctuations and a large static offset, consistent with previous studies of the binary complexes of this enzyme. These results show that PAAD(+) is an excellent probe of local dynamics and that it should be a general tool for probing the dynamics of a wide range of NAD-dependent enzymes.

Overexpression of a wheat jasmonate-regulated lectin increases pathogen resistance.

Jasmonates are known to induce the transcriptional activation of plant defense genes, which leads to the production of jasmonate-regulated proteins (JRP). We previously cloned and characterized a novel jacalin-like lectin gene (Ta-JA1) from wheat (Triticum aestivum L.), which codes a modular JRP with disease response and jacalin-related lectin (JRL) domains and is present only in the Gramineae family. The function of this protein is still unclear. Phylogenetic analysis indicated that Ta-JA1 and related proteins from cereals grouped together, which diverged from JRL with an additional N-terminal disease response domain. The recombinant Ta-JA1 proteins agglutinated rabbit erythrocytes, and this hemagglutination activity was preferentially inhibited by mannose. The Ta-JA1 protein was able to inhibit E. coli cell growth. Overexpression of Ta-JA1 in transgenic tobacco plants increased their resistance to infection by tobacco bacterial, fungal and viral pathogens. Our results suggest that Ta-JA1 belongs to a mannose-specific lectin, which may confer a basal but broad-spectrum resistance to plant pathogens. Ta-JA1 and its homologues in maize, rice, sorghum and creeping bentgrass may represent a new type of monocot lectin with a modular structure and diversity of physiological functions in biotic and abiotic stress responses.

[Comparison of chlorophyll a concentration estimation in Taihu Lake using different methods].

Based on the measured remote sensing reflectance and concurrent chlorophyll a (Chl-a) concentration in Taihu Lake from January 7 to 9 and July 29 to August 1, 2006, this study comparatively analyzed the estimation precision of three-band-model, two-band-model, reflectance peak position method and first derivative method, and further discussed the feasibility of the four methods to estimate Chl-a using remote sensing image. The data set of two samplings contained widely variable total suspended matter (12.24-285.20 mg x L(-1), Chl-a (4.83-155.11 microg x L(-1)) and chromophoric dissolved organic matte absorption coefficient at 440 nm (0.27-2.36 m(-1)). The former four methods all got high precisions on Chl-a concentration estimation in Taihu Lake with determination coefficients (r2) of 0.813, 0.838, 0.872 and 0.819, respectively. The root mean square error (RMSE) between measured and estimated Chi-a concentrations using the four models was 13.04, 12.12, 13.41 and 12.13 microg x L(-1), respectively, and the relatively error (RE) was 35.5%, 34.9%, 24.6% and 41.8%, respectively. Although the reflectance peak position method had the highest estimation precision, it was difficult to be applied on remote sensing image due to lacking spectral channel. The three-band-model and two-band-model had higher estimation precisions than the first order differential method and good application foreground in Chl-a retrieval using remote sensing image. The r2, RMSE, RE of [R(-1) (665)- R(-1) (709)] x R(754) in three-band-model and R(709)/R(681) in two-band-model based on simulation MERIS data were 0.788, 13.87 microg x L(-1), 37.3%, and 0.815, 12.96 microg x L(-1), 34.8%, respectively. The results in this study demonstrated MERIS data could be applied to retrieve Chl-a concentration in turbid Case-II waters as Taihu Lake.

[Transmission disequilibrium test for nonsyndromic cleft lip and palate and segment homeobox gene-1 gene].

OBJECTIVE: To investigate the relationship between muscle segment homeobox gene-1 (MSX1) and the genetic susceptibility of nonsyndromic cleft lip and palate (NSCLP) in Hunan Hans. METHODS: One microsatellite DNA marker CA repeat in MSX1 intron region was used as genetic marker. The genotypes of 387 members in 129 NSCLP nuclear family trios were analyzed by polymerase chain reaction (PCR) and denaturing polyacrylamide gel electrophoresis. Then transmission disequilibrium test (TDT) and Logistic regression analysis were used to conduct association analysis. RESULTS: TDT analysis confirmed that CA4 allele in CL/P and CPO groups preferentially transmitted to the affected offspring (P = 0.018, P = 0.041). Logistic regression analysis indicated that the recessive model of inheritance was supported, and CA4 itself or CA4 acting as a marker for a disease allele or haplotype was inherited in a recessive fashion (P = 0.009). CONCLUSIONS: MSX1 gene is associated with NSCLP, and MSX1 gene may be directly involved either in the etiology of NSCLP or in linkage disequilibrium with disease-predisposing sites.

[Association study on microsatellite polymorphisms of MSX1 gene and nonsyndromic cleft lip and palate].

OBJECTIVE: To investigate muscle segment homeobox 1 (MSX1) microsatellite marker distribution and the relationship between MSX1 gene and the genetic susceptibility of nonsyndromic cleft lip and palate (NSCLP) in Hunan Hans. METHODS: One microsatellite DNA marker CA repeat in MSX1 intron region was used as genetic markers. The genotypes of 129 patients with NSCLP and 108 controls were analyzed by the techniques of polymerase chain reaction (PCR) and denaturing polyacrylamide gel electrophoresis (PAGE). Then case-control study was used to conduct association analysis. RESULTS: The allele frequencies of the CA repeat microsatellite DNA in Hunan Han normal population were in good agreement with Hardy-Weinberg equilibrium. The polymorphism information content and heterozygosity of CA repeat microsatellite DNA were 0.50 and 0.50 respectively. The allele CA4 frequency in CL/P and CPO group was significantly higher than that of normal controls (P<0.05). The genotype CA4,4 frequency was significantly higher in CL/P and CPO group than that in normal controls (P<0.05). CONCLUSION: The microsatellite DNA marker CA repeat in MSX1 is a good genetic marker. MSX1 gene is significantly associated with NSCLP in Hunan Hans.

[Association between retinoic acid receptor alpha gene polymorphisms and nonsyndromic cleft lip with or without cleft palate susceptibility].

OBJECTIVE: To investigate the relationship between D17S579 microsatellite marker allelic polymorphisms in retinoic acid receptor-alpha (RARA) gene and the genetic susceptibility to nonsyndromic cleft lip with or without cleft palate (NSCL/P) in Hunan Hans. METHODS: PCR and denaturing polyacrylamide gel electrophoresis (PAGE) were used to detect the polymorphism of RARA gene marked by D17S579 among 140 patients with NSCL/P, 82 males and 58 females, aged 3 months-14 years, and 132 healthy persons, 68 males and 64 females, aged 6 months-14 years, who underwent physical examination. RESULTS: The A6 allele frequency of the NSCL/P patients was 8.93%, significantly higher than that of the healthy persons (4.17%, P = 0.026). The A9 allele frequency the NSCL/P patients was 13.21%, significantly higher than that of the healthy persons (5.68%, P = 0.003). There were not significant differences in the frequencies of different alleles between the patients with family history and the patients without family history (chi2 = 2.710, P = 0.978). CONCLUSION: The A6 and A9 alleles in D17S579 microsatellite marker of RARA gene may be correlated with the development of NSCL/P in Hunan Hans. There is no association between the family history and RARA polymorphism in the NSCL/P patients.

[p53 gene intron 7 polymorphism and its association with oral neoplasms].

OBJECTIVE: To investigate the association between oral neoplasm genetic susceptibility and genetic polymorphism of p53 intron 7. METHODS: The intron 7 ApaI polymorphism of p53 was analyzed in 95 oral neoplasm patients and 105 healthy individuals by utilizing polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) genotyping assay technique, and direct sequencing was performed in 30 cases which were selected from the patients and controls by random sampling. RESULTS: In oral neoplasms cases, haplotype combinations were T-G 43.2%, C-T 56.8%, and frequencies of genotype were T-G/T-G 15.8%, C-T/T-G 54.7%, C-T/C-T 29.5%, while in controls they were T-G 30.9%, C-T 69.1% and T-G/T-G 10.5%, C-T/T-G 41.0%, C-T/C-T 48.5%. There was a significant difference in the allelic frequency and the genotypical distributions between the oral neoplasm patients and the controls. The individuals with the T-G allele had a slight increasing neoplasm risk than individuals with C-T allele; the OR for T-G versus C-T was 1.69 (95% CI, 1.12 - 2.51). The risk of suffering from oral neoplasms was higher in the individuals of T-G/T-G genotype and of T-G/C-T genotype than in individuals of C-T/CT genotype with odds ratio of 2.48 versus 2.20. CONCLUSIONS: There are two polymorphic points in the 7th intron of human p53 gene, which could be associated with genetic susceptibility of oral neoplasms. T-G allele may be the risk factor of oral neoplasms.

Water-catalyzed O-H insertion/HI elimination reactions of isodihalomethanes (CH2X-I, where X = Cl, Br, I) with water and the dehalogenation of dihalomethanes in water-solvated environments.

A combined experimental and theoretical investigation of the ultraviolet photolysis of CH2XI (where X = Cl, Br, I) dihalomethanes in water is presented. Ultraviolet photolysis of low concentrations of CH2XI (where X = Cl, Br, I) in water appears to lead to almost complete conversion into CH2(OH)2 and HX and HI products. Picosecond time-resolved resonance Raman (ps-TR3) spectroscopy experiments revealed that noticeable amounts of CH2X-I isodihalomethane intermediates were formed within several picoseconds after photolysis of the CH2XI parent compound in mixed aqueous solutions. The ps-TR3 experiments in mixed aqueous solutions revealed that the decay of the CH2X-I isodihalomethane intermediates become significantly shorter as the water concentration increases, indicating that the CH2X-I intermediates may be reacting with water. Ab initio calculations found that the CH2X-I intermediates are able to react relatively easily with water via a water-catalyzed O-H insertion/HI elimination reaction to produce CH2X(OH) and HI products, with the barrier for these reactions increasing as X changes from Cl to Br to I. The ab initio calculations also found that the CH2X(OH) product can undergo a water-catalyzed HX elimination reaction to make H2C=O and HX products, with the barrier to reaction decreasing as X changes from Cl to Br to I. The preceding two water-catalyzed reactions produce the HI and HX leaving groups observed experimentally, and the H2C=O product further reacts with water to make the other CH2(OH)2 product observed in the photochemistry experiments. This suggests that that the CH2X-I intermediates react with water to form the CH2(OH)2 and HI and HX products observed in the photochemistry experiments. Ultraviolet photolysis of CH2XI (where X = Cl, Br, I) at low concentrations in water-solvated environments appears to lead to efficient dehalogenation and release of two strong acid leaving groups. We very briefly discuss the potential influence of this photochemistry in water on the decomposition of polyhalomethanes and halomethanols in aqueous environments.

Ultraviolet photolysis of CH2I2 in methanol: O-H insertion and HI elimination reactions to form a dimethoxymethane product.

Ultraviolet photolysis of low concentrations of CH2I2 in methanol solution found that CH2I2 is converted into dimethoxymethane and some H+ and I- products. Picosecond time-resolved resonance Raman (ps-TR3) experiments observed that the isodiiodomethane (CH2I-I) photoproduct decayed faster as the concentration of methanol increases, suggesting that isodiiodomethane is reacting with methanol. Ab initio calculations indicate isodiiodomethane is able to react with methanol via an O-H insertion/HI elimination to form an iodoether (ICH2-O-CH3) and HI products. The iodoether can then further react via another O-H insertion/HI elimination reaction to form the dimethoxymethane (CH3-O-CH2-O-CH3) observed in the photochemistry experiments. A reaction mechanism consistent with these experimental and theoretical observations is proposed.

Comparison of the dehalogenation of polyhalomethanes and production of strong acids in aqueous and salt (NaCl) water environments: Ultraviolet photolysis of CH(2)I(2).

The ultraviolet photolysis of CH(2)I(2) was studied in water and salt water solutions using photochemistry and picosecond time-resolved resonance Raman spectroscopy. Photolysis in both types of environments produces mainly CH(2)(OH)(2) and HI products. However, photolysis of CH(2)I(2) in salt water leads to the formation of different products/intermediates (CH(2)ICl and Cl(2) (-)) not observed in the absence of salt in aqueous solutions. The amount of CH(2)(OH)(2) and HI products appears to decrease after photolysis of CH(2)I(2) in salt water compared to pure water. We briefly discuss possible implications of these results for photolysis of CH(2)I(2) and other polyhalomethanes in sea water and other salt aqueous environments compared to nonsalt water solvated environments.

Efficient dehalogenation of polyhalomethanes and production of strong acids in aqueous environments: water-catalyzed O--H-insertion and HI-elimination reactions of isodiiodomethane (CH2I-I) with water.

A combined experimental and theoretical study of the ultraviolet photolysis of CH2I2 in water is reported. Ultraviolet photolysis of low concentrations of CH2I2 in water was experimentally observed to lead to almost complete conversion into CH2(OH)2 and 2HI products. Picosecond time-resolved resonance Raman spectroscopy experiments in mixed water/acetonitrile solvents (25%-75% water) showed that appreciable amounts of isodiiodomethane (CH2I-I) were formed within several picoseconds and the decay of the CH2I-I species became substantially shorter with increasing water concentration, suggesting that CH2I-I may be reacting with water. Ab initio calculations demonstrate the CH2I-I species is able to react readily with water via a water-catalyzed O--H-insertion and HI-elimination reaction followed by its CH2I(OH) product undergoing a further water-catalyzed HI-elimination reaction to make a H2C=O product. These HI-elimination reactions produce the two HI leaving groups observed experimentally and the H2C=O product further reacts with water to produce the other final CH2(OH)2 product observed in the photochemistry experiments. These results suggest that CH2I-I is the species that reacts with water to produce the CH2(OH)2 and 2HI products seen in the photochemistry experiments. The present study demonstrates that ultraviolet photolysis of CH2I2 at low concentration leads to efficient dehalogenation and release of multiple strong acid (HI) leaving groups. Some possible ramifications for the decomposition of polyhalomethanes and halomethanols in aqueous environments as well as the photochemistry of polyhalomethanes in the natural environment are briefly discussed.

Direct observation of an isopolyhalomethane O-H insertion reaction with water: picosecond time-resolved resonance Raman (ps-TR3) study of the isobromoform reaction with water to produce a CHBr2OH product.

Picosecond time-resolved resonance Raman (ps-TR3) spectroscopy was used to obtain the first definitive spectroscopic observation of an isopolyhalomethane O-H insertion reaction with water. The ps-TR3 spectra show that isobromoform is produced within several picoseconds after photolysis of CHBr3 and then reacts on the hundreds of picosecond time scale with water to produce a CHBr2OH reaction product. Photolysis of low concentrations of bromoform in aqueous solution resulted in noticeable formation of HBr strong acid. Ab initio calculations show that isobromoform can react with water to produce a CHBr2(OH) O-H insertion reaction product and a HBr leaving group. This is consistent with both the ps-TR3 experiments that observe the reaction of isobromoform with water to form a CHBr2(OH) product and photolysis experiments that show HBr acid formation. We briefly discuss the implications of these results for the phase dependent behavior of polyhalomethane photochemistry in the gas phase versus water solvated environments.

Water-catalyzed dehalogenation reactions of isobromoform and its reaction products.

A combined experimental and theoretical study of the photochemistry of CHBr(3) in pure water and in acetonitrile/water mixed solvents is reported that elucidates the reactions and mechanisms responsible for the photochemical conversion of the halogen atoms in CHBr(3) into three bromide ions in water solution. Ultraviolet excitation at 240 nm of CHBr(3) (9 x 10(-)(5) M) in water resulted in almost complete conversion into 3HBr leaving groups and CO (major product) and HCOOH (minor product) molecules. Picosecond time-resolved resonance Raman (ps-TR(3)) experiments and ab initio calculations indicate that the water-catalyzed O-H insertion/HBr elimination reaction of isobromoform and subsequent reactions of its products are responsible for the production of the final products observed following ultraviolet excitation of CHBr(3) in water. These results have important implications for the phase-dependent behavior of polyhalomethane photochemistry and chemistry in water-solvated environments as compared to gas-phase reactions. The dissociation reaction of HBr into H(+) and Br(-) ions is the driving force for several O-H insertion and HBr elimination reactions and allows O-H and C-H bonds to be cleaved more easily than in the absence of water molecules. This water-catalysis by solvation of a leaving group and its dissociation into ions (e.g., H(+) and Br(-) in the examples investigated here) may occur for a wide range of chemical reactions taking place in water-solvated environments.