Molecular Dynamics Simulations of Melting Iron Nanoparticles with/without Defects Using a Reaxff Reactive Force Field.

Molecular dynamics simulations are performed to study thermal properties of bulk iron material and Fe nanoparticles (FNP) by using a ReaxFF reactive force field. Thermodynamic and energy properties such as radial distribution function, Lindemann index and potential energy plots are adopted to study the melting behaviors of FNPs from 300 K to 2500 K. A step-heating method is introduced to obtain equilibrium melting points. Our results show ReaxFF force field is able to detect size effect in FNP melting no matter in energy or structure evolution aspect. Extra storage energy of FNPs caused by defects (0%-10%) is firstly studied in this paper: defects will not affect the melting point of FNPs directly but increase the system energy especially when temperature reaches the melting points.

Mutations in algal and cyanobacterial Photosystem I that independently affect the yield of initial charge separation in the two electron transfer cofactor branches.

In Photosystem I, light-induced electron transfer can occur in either of two symmetry-related branches of cofactors, each of which is composed of a pair of chlorophylls (ec2A/ec3A or ec2B/ec3B) and a phylloquinone (PhQA or PhQB). The axial ligand to the central Mg2+ of the ec2A and ec2B chlorophylls is a water molecule that is also H-bonded to a nearby Asn residue. Here, we investigate the importance of this interaction for charge separation by converting each of the Asn residues to a Leu in the green alga, Chlamydomonas reinhardtii, and the cyanobacterium, Synechocystis sp. PCC6803, and studying the energy and electron transfer using time-resolved optical and EPR spectroscopy. Nanosecond transient absorbance measurements of the PhQ to FX electron transfer show that in both species, the PsaA-N604L mutation (near ec2B) results in a ~50% reduction in the amount of electron transfer in the B-branch, while the PsaB-N591L mutation (near ec2A) results in a ~70% reduction in the amount of electron transfer in the A-branch. A diminished quantum yield of P700+PhQ- is also observed in ultrafast optical experiments, but the lower yield does not appear to be a consequence of charge recombination in the nanosecond or microsecond timescales. The most significant finding is that the yield of electron transfer in the unaffected branch did not increase to compensate for the lower yield in the affected branch. Hence, each branch of the reaction center appears to operate independently of the other in carrying out light-induced charge separation.

The Presence of the IsiA-PSI Supercomplex Leads to Enhanced Photosystem I Electron Throughput in Iron-Starved Cells of Synechococcus sp. PCC 7002.

Photosystem I (PS I) is highly demanding of iron, requiring 12 atoms in the bound FX, FB, and FA iron-sulfur clusters and two atoms in the mobile acceptor protein ferredoxin. When grown under iron-limiting conditions, certain cyanobacteria express IsiA, a peripheral chlorophyll a antenna protein, and IsiB, a flavodoxin that substitutes for ferredoxin. The IsiA protein forms single and double rings around PS I, presumably to increase the optical cross-section so as to compensate for fewer PS I complexes. Previous studies have shown that IsiA serves as an efficient light-harvesting structure ( Andrizhievskaya , G. G. ; et al. Biochim. Biophys. Acta 2002 , 1556 , 262 - 272 ); however, few, if any, studies have been carried out to show that the increased optical cross-section leads to an enhanced rate of electron transfer through PS I. Here, we report a more rapid transient accumulation of the A1(-) phyllosemiquinone anion radical by EPR spectroscopy in dark-adapted iron-depleted cells than in iron-replete cells after a block of intense light. A derivative-shaped optical signal in the light-minus-dark difference spectrum of PS I from an electrochromic bandshift of a carotenoid located near the A1 phylloquinones is enhanced in iron-depleted wild-type cells and in an iron-depleted isiB deletion strain, which lacks flavodoxin, but is greatly diminished in an iron-depleted isiA deletion strain, which lacks IsiA and flavodoxin. These findings indicate that the transient accumulation of electrons on A1 occurs more rapidly in the IsiA/PS I supercomplex than in the PS I complex alone. Thus, the increased absorption cross-section from the IsiA proteins translates directly to an enhanced rate of electron transfer through PS I.

Species-dependent alteration of electron transfer in the early stages of charge stabilization in Photosystem I.

Electron transfer (ET) in Photosystem I (PS I) is bidirectional, occurring in two pseudosymmetric branches of cofactors. The relative use of two branches in the green alga Chlamydomonas reinhardtii and the cyanobacterium Synechocystis sp. PCC 6803 has been studied by changing the Met axial ligands of the chlorophyll a acceptor molecules, A0A and A0B, to His. The nature of the effect on the ET is found to be species dependent. In C. reinhardtii, transient absorption and transient EPR data show that in the M688HPsaA variant, forward ET from A0A to the quinone, A1A, is blocked in 100% of the PS I complexes. In contrast, in Synechocystis sp. PCC 6803, forward ET from A0A to A1A is blocked in only 50% of the PS I complexes, but in those PS I complexes in which electrons reach A1A, further transfer to the iron-sulfur cluster FX is blocked. Similar species differences are found for the corresponding B-branch variants. One possible explanation of this behavior is that it is the result of two conformers in which an H-bond between the His side chain and the O1 carbonyl group of A1 is either present or absent. The spectroscopic data suggest that the two conformers are present in nearly equal amounts in the Synechocystis sp. PCC 6803 variants, while only the conformer without the H-bond is present in the same variants of C. reinhardtii.

Longitudinal change in end-digit preference in blood pressure recordings of patients with hypertension in primary care clinics: Minhang study.

BACKGROUND: End-digit preference (EDP) of blood pressure (BP) has been reported in both general hospitals and primary clinics worldwide. We aimed to observe the longitudinal changes in EDP of BP recordings in hypertension patients and to estimate the impact of hypertension treatment target (140/90 mmHg) on the EDP of BP in Chinese primary care clinics. PARTICIPANTS AND METHODS: A total of 318 898 BP readings from 16 433 hypertensive patients were obtained from the electronic health record of Xinzhuang town hospital in Shanghai from 1 January 2007, to 27 September 2011. The terminal digits of the recorded systolic blood pressure (SBP) and diastolic blood pressure (DBP) were analyzed. Zero preference was also analyzed according to the year and follow-ups, respectively. RESULTS: In all, 62.5% of SBP readings and 63.5% of DBP readings ended in zero. The zero preference of SBP was reduced from the 75.2% in 2007 to 55.9% in 2011. In addition, the zero preference decreased from the 78.6% at the registration to 58.7% at the 25th follow-up. Moreover, compared with other BP levels, hypertension treatment target was associated with increased preference for the eight end-digit for both SBP and DBP (P<0.001). CONCLUSION: This study showed a decrease in zero EDP in hypertension patients managed in the Chinese community. The hypertension treatment target was associated with sub-target-EDP. Future efforts should focus on comprehensive education, coupled with the use of well-calibrated electronic BP monitors.

Use of home blood pressure monitoring among hypertensive adults in primary care: Minhang community survey.

BACKGROUND: Several evidences have supported the benefits of home blood pressure monitoring (HBPM) in improving hypertension awareness and control. However, little was known about the use of HBPM by hypertensive patients in primary care in China. MATERIALS AND METHODS: A cross-sectional questionnaire survey on HBPM use was conducted on 1915 hypertensive patients in Xinzhuang County Hospital in Shanghai, and the factors related to regular use of HBPM were also determined. RESULTS: Overall, 1011 of the 1915 participants engaged in using HBPM, among whom 786 individuals used HBPM more than once a month. Of the 1011 HBPM users, 25.42% chose a mercury sphygmomanometer, 33.55% used wrist-cuff electronic devices, and 46.5% selected arm-cuff electronic devices. In addition, 73% of HBPM users reported HBP readings to their general practitioners. Compared with the less frequent users, patients who used HBPM daily were likely to report their blood pressure (BP) values to the doctors depending on notebook or mechanical memory than on their own memories (P<0.001). Moreover, patients with college education were 2.7 times more likely than those with middle school education or less to engage in frequent HBPM use (odds ratio=2.71, 95% confidence interval=2.03-3.61). CONCLUSION: This local community survey showed that ∼40% of hypertension patients used HBPM frequently in primary care in China. However, certain patients chose the improper BP monitoring device or questionable reporting methods. Therefore, the use of arm-cuff electric devices with multiple memory storage or a home BP telemonitoring system should be promoted by health education targeted at hypertensive patients.

Evidence that histidine forms a coordination bond to the A(0A) and A(0B) chlorophylls and a second H-bond to the A(1A) and A(1B) phylloquinones in M688H(PsaA) and M668H(PsaB) variants of Synechocystis sp. PCC 6803.

The axial ligands of the acceptor chlorophylls, A(0A) and A(0B), in Photosystem I are the Met sulfur atoms of M688(PsaA) and M668(PsaB). To determine the role of the Met, His variants were generated in Synechocystis sp. PCC 6803. Molecular dynamics simulations on M688H(PsaA) show that there exist low energy conformations with the His coordinated to A(0A) and possibly H-bonded to A(1A). Transient EPR studies on M688H(PsaA) indicate a more symmetrical electron spin distribution in the A(1A) phyllosemiquinone ring consistent with the presence of an H-bond to the C1 carbonyl. Ultrafast optical studies on the variants show that the 150fs charge separation between P700 and A(0) remains unaffected. Studies on the ns timescale show that 57% of the electrons are transferred from A(0A)(-) to A(1A) in M688H(PsaA) and 48% from A(0B)(-) to A(1B) in M668H(PsaB); the remainder recombine with P700(+) with 1/e times of 25ns and 37ns, respectively. Those electrons that reach A(1A) and A(1B) in the branch carrying the mutation are not transferred to FX, but recombine with P700(+) with 1/e times of ~15µs and ~5µs, respectively. Hence, the His is coordinated to A0 in all populations, but in a second population, the His may be additionally H-bonded to A(1). Electron transfer from A(0) to A(1) occurs only in the latter, but the higher redox potentials of A(0) and A(1) as a result of the stronger coordination bond to A(0) and the proposed second H-bond to A(1) preclude electron transfer to the Fe/S clusters.

Association of body mass index with cause specific deaths in Chinese elderly hypertensive patients: Minhang community study.

BACKGROUND: Most studies have suggested that elevated body mass index (BMI) was associated with the risk of death from all cause and from specific causes. However, there was little evidence illustrating the effect of BMI on the mortality in elderly hypertensive patients in Chinese population. METHODS: The information of 10,957 hypertensive patients at baseline not less than 60 years were from Xinzhuang, a town in Minhang district of Shanghai, was extracted from the Electronic Health Record (EHR) system. All study participants were divided into eight categories of baseline BMI (with cut-points at 18, 20, 22, 24, 26, 28 and 30 kg/m(2)). Relative hazard ratio of death from all cause, cardiovascular and non-cardiovascular cause by baseline BMI groups were calculated, standardized for sex, age, smoking, drinking, physical activity, systolic blood pressure, history of cardiovascular disorders, serum lipid disturbance, diabetes mellitus and antihypertensive drug treatment. RESULTS: DURING FOLLOW UP (MEDIAN: 3.7 years), 561 deaths occurred. Underweight (BMI<18 kg/m(2)) was associated with significantly increased mortality from all cause mortality (OR: 2.00; 95% CI: 1.43-2.79) and non cardiovascular mortality (OR: 2.76; 95% CI: 1.87-4.07), but not with cardiovascular mortality. For the cause specific analysis, the underweight was associated significantly with neoplasms (OR: 2.15; 95% CI: 1.16-4.00) and respiratory disorders (OR: 3.41; 95% CI: 1.64-7.06). The results for total mortality and specific cause mortality were not influenced by sex, age and smoking status. CONCLUSION: Our study revealed an association between underweight and increased mortality from non-cardiovascular disorders in elderly hypertensive patients in Chinese community. Overweight and obesity were not associated with all cause or cause specific death.

Macrophage migration inhibitory factor (MIF) interacts with Bim and inhibits Bim-mediated apoptosis.

The pro-apoptotic Bcl-2 family member Bim acts as a sensor for apoptotic stimuli and initiates apoptosis through the mitochondrial pathway. To identify novel regulators of Bim, we employed the yeast two-hybrid system and isolated the human gene encoding macrophage migration inhibitory factor (MIF), a ubiquitously expressed proinflammatory mediator that has also been implicated in cell proliferation, the cell cycle and carcinogenesis. The interaction between MIF and Bim was confirmed by both in vitro and in vivo protein interaction assays. Intriguingly, protein complexes between MIF and the three major Bim isoforms (BimEL/BimL/BimS) could be detected in HEK293 and K562 cells, especially in cells undergoing apoptosis. Moreover, exogenous expression of MIF partially inhibited Bim-induced apoptosis in HEK293 cells. SiRNA-mediated knockdown of MIF increased apoptosis in K562 cells exposed to the chemical oxidant diamide. Endogenous MIF may regulate the pro-apoptotic activity of Bim and inhibit the release of cytochrome c from mitochondria.