[Eco-physiological functions of soil microbial biofilms: A review]. / åœŸå£¤å¾®ç”Ÿç‰©è†œç”Ÿç†ç”Ÿæ€åŠŸèƒ½ç ”ç©¶è¿›å±•.

Soil microbial biofilms (SMBs) are a biological community of soil bacteria and their accumulative extracellular polymeric substances (EPS), which are the initial status and the most important components of biological soil crusts. SMBs, as the most common mode of soil bacterium survival, not only greatly contribute to the survival of free-living cells, but also stick to soil particles and roots, performing a variety of important ecological functions. Based on the structure and composition analysis of SMBs, we gave a summary of eco-physiological functions of SMBs involving soil quality and plant health. SMBs have higher metabolic activity than free-living cells. It promotes EPS secretion and organic turnover, which is important for soil fertility, pollutant decomposition, and aggregate formation. SMBs help improve plant nutrient utilization and stress resistance through the synergy of microorganisms, promotion of plant growth, promoting substance secretion and immobilization of EPS. In the future, it will be critical to uncover the micro-mechanisms underlying SMBs' eco-physiological functions and to screen functional soil bacterium strains.

Surgical treatment for both-column acetabular fractures using pre-operative virtual simulation and three-dimensional printing techniques.

BACKGROUND: Surgical treatment of both-column acetabular fractures is challenging because of the complex acetabular fracture patterns and the curved surface of the acetabulum. Seldom study has compared the application of three-dimensional (3D) printing technology and traditional methods of contouring plates intra-operatively for the surgical treatment of both-column acetabular fractures. We presented the use of both 3D printing technology and a virtual simulation in pre-operative planning for both-column acetabular fractures. We hypothesized that 3D printing technology will assist orthopedic surgeons in shortening the surgical time and improving the clinical outcomes. METHODS: Forty patients with both-column acetabular fractures were recruited in the randomized prospective case-control study from September 2013 to September 2017 for this prospective study (No. ChiCTR1900028230). We allocated the patients to two groups using block randomization (3D printing group, n = 20; conventional method group, n = 20). For the 3D printing group, 1:1 scaled pelvic models were created using 3D printing, and the plates were pre-contoured according to the pelvic models. The plates for the conventional method group were contoured during the operation without 3D printed pelvic models. The operation time, instrumentation time, time of intra-operative fluoroscopy, blood loss, number of times the approach was performed, blood transfusion, post-operative fracture reduction quality, hip joint function, and complications were recorded and compared between the two groups. RESULTS: The operation and instrumentation times in the 3D printing group were significantly shorter (130.8 ±â€Š29.2 min, t = -7.5, P < 0.001 and 32.1 ±â€Š9.5 min, t = -6.5, P < 0.001, respectively) than those in the conventional method group. The amount of blood loss and blood transfusion in the 3D printing group were significantly lower (500 [400, 800] mL, Mann-Whitney U = 74.5, P < 0.001 and 0 [0,400] mL, Mann-Whitney U = 59.5, P < 0.001, respectively) than those in the conventional method group. The number of the approach performed in the 3D printing group was significantly smaller than that in the conventional method group (pararectus + Kocher-Langenbeck [K-L] approach rate: 35% vs. 85%; χ = 10.4, P < 0.05). The time of intra-operative fluoroscopy in the 3D printing group was significantly shorter than that in the conventional method group (4.2 ±â€Š1.8 vs. 7.7 ±â€Š2.6 s; t = -5.0, P < 0.001). The post-operative fracture reduction quality in the 3D printing group was significantly better than that in the conventional method group (good reduction rate: 80% vs. 30%; χ = 10.1, P < 0.05). The hip joint function (based on the Harris score 1 year after the operation) in the 3D printing group was significantly better than that in the conventional method group (excellent/good rate: 75% vs. 30%; χ = 8.1, P < 0.05). The complication was similar in both groups (5.0% vs. 25%; χ = 3.1, P = 0.182). CONCLUSIONS: The use of a pre-operative virtual simulation and 3D printing technology is a more effective method for treating both-column acetabular fractures. This method can shorten the operation and instrumentation times, reduce blood loss, blood transfusion and the time of intra-operative fluoroscopy, and improve the post-operative fracture reduction quality. CLINICAL TRAIL REGISTRATION: No.ChiCTR1900028230; http://www.chictr.org.cn.

Photo induced reaction of myoglobins with energy transferred from excited free tryptophan.

Despite being one of the most studied proteins in biology, the photolysis mechanism of myoglobin heme affected by endogenous substances free amino acids is still in controversy. The transient absorption and kinetic processes of photo-excited myoglobin in three forms and the effects of free excited tryptophan on redox reaction of myoglobin were monitored by laser flash photolysis. With dual energy superposition of direct light irradiation and indirect energy transferred from the free excited tryptophan, the variation value in optical density (ΔOD) of MetMb increased by 66.7%, from 0.9 to 1.5. The ΔOD value of MbO2 in ferrous form increased from 0.9 to 1.25, while the ΔOD value of DeoxyMb increased from 0.75 to 1.2. The decay time of excited DeoxyMb was prolonged obviously with the excited tryptophan, while the decay time of excited MbO2 and MetMb was shortened significantly. The excited tryptophan could promote laser induced reaction processes of myoglobin in different forms by intermolecular energy transfer to one final similar photo reaction state. The possible photo induced reaction mechanisms of DeoxyMb, MbO2, MetMb with and without free tryptophan were also proposed.

Stoichiometric characteristics of nitrogen and phosphorus in leaf-litter-soil system of Pinus sylvestris var. mongolica plantations.

To reveal the allocation pattern and stoichiometric characteristics of N and P in Pinus sylvestris var. mongolica plantation, we selected three P. sylvestris plantation with different stand ages (middle-aged, near-mature, mature) in the Hulunbuir, Horqin, and Mu Us sandy land as objects, and analyzed the contents of nitrogen, phosphorus and the N:P stoichiometry ratios in the leaf, litter, and soil. The results showed that the contents of N, P and N/P ratios in leaf, litter and soil varied in the range of 0.17-49.02, 0.11-3.01 g·kg-1 and 0.51-19.74, respectively, with the order of leaf>litter>soil. The content of N and N:P ratio were significantly different between leaf, litter and soil; the P content in leaf was significantly higher than that in litter and soil. The different areas and stand ages affected N, P content and N/P stoichiometry ratio, but the interaction of area and stand age had no significant effect on N/P stoichiometry ratio. The N, P contents in leaf, litter and soil increased with stand age, and were highest in the mature forest. The contents of N, P and N/P ratios were significantly positively correlated among the leaf, litter and soil. In the Hulunbuir and Horqin sandy land, the N/P ratros of leaf were between 14.53 to 15.57, which indicated that the P. sylvestris var. mongolica plantations was restricted by both N and P availability. In Mu Us sand land, the N:P ratios of leaf were between 18.56 to 19.71, which indicated P limitation. The stand age had no significant influence on soil N and P limitation. To improve the productivity of P. sylvestris var. mongolica plantations, we could appropriately add N or P fertilization in the plantation tending management based on local conditions. Our findings could contribute to a further understanding of the mechanism of interactions and constraints between N and P in the leaf-litter-soil system of P. sylvestris var. mongolica plantations, and provide a scientific guidance for the management.

Spectroscopic insights into the Photoreduction of Cytochrome c with UVA-Vis Light Irradiation.

With the particular conjugation structure in the heme prosthetic group, Cyt c shows unusual functions similar to chlorophyll while irradiated by specific wavelength of UV-Vis lights. To further reveal mechanism of the photo-irradiation of Cyt c, we then studied various external factors that may influence the photo induced process. The absorbance intensity increase of band (317 nm) and Q band (520 nm and 549 nm)indicated Cyt c in phosphate-buffered saline within N2 atmosphere was photoreduced to Fe(II) Cyt c. Irradiated by 410 nm, the photoreduction process was facilitated by Met. But Trp, Tyr and Phe impeded the process due to their light absorbance abilities. In addition, the results of fluorescence and CD spectra indicated that the microenvironment polarity of Trp residue varied during the photoreduction process. And the secondary structure of Cyt c changed with lower α-helix/ßsheet ratio. The photoreduction mechanism of Cyt c was intramolecular electron transfer and porphyrin cation radicals were generated. The protein structure of Cyt c changed as well as part of the photoreduction.

[Spectral Study on Coordination Reaction Between metMyoglobin and Nitric Oxide].

As we all known, the instantaneous reaction between protein and ligands are very important to adjust the normal playing of biological function. And nitric oxide interactions with iron are the most important biological reactions in which NO participates. Unlike carbon monoxide or oxygen, NO can also bind reversibly to ferric iron. In this paper, UV-Vis absorption and CD spectra were used to study coordination reaction process between horse heart metMb and NO, to demonstrate the coordination reaction mechanism and to explore the influencing factors of metMb with NO. The experimental results showed that metMb could react with NO, and obtained three new peaks at 420 nm, 534 and 568 nm, respectively, which implied metMb and NO have reacted and generated a new complex-nitrosylmetmyoglobin (metMbNO). Then as time went on, NO concentration decreased in the solution, and the Fe-N bond fractured under the attack of H2O, then NO leaves slowly from metMbNO, and met-Mb was regenerated. In this experiment, we also found that external conditions such as buffer medium, ionic strength, pH, temperature, etc, had an important influence on the coordination reaction between metMb and NO. It was favorable for the coordination reaction, when the 0.01 mol x L(-1) phosphate buffer. solution is near neutral condition, the temperature is 280 K, the coordination reaction could reach equilibrium at a fastest speed. In addition, the CD date show that NO only reacts with Fe atom in the center of heme and has less effect on the secondary structuers of protein. The research of metMb and NO played an important role to further study the function of NO. Especially the establish of equilibrium reaction mechanism between NO and heme protein has an important research value on maintaining the balance of NO in vivo and keeping the normal function in the body's cells.

[DFT/TDDFT study on the structure and absorption spectra of free base, N-/neo-confused porphyrin].

Porphyrin is an important class of photochemical materials, which has been widely used in various fields. Computational investigations into the ground state structures and orbital energy levels of free base porphyrin (FBP), neo-confused porphyrin (NECP) and N-confused porphyrin (NCP) were performed with density functional theory(DFT). Absorption spectra were calculated at TD-B3LYP/6-31+G(d). Degeneracy of HOMO and HOMO-1 is lost, which would account for the shoulder peaks about the most intense transitions of FBP and NECP. Following FBP, NECP and NCP order, the orbital energy level (OEL) of LUMO decreases while the OEL of HOMO increases, which lead to the red shift of adsorption spectra. The energy difference between LUMO and LUMO+1 is almost the same as the difference between HOMO and HOMO-1, which would account for the only most intense transition of NCP. Solvent effect on ground state structures and absorption spectra was also investigated. The data shows that the character peak of Soret band and Q band changes in different solvent (benzene, chloroform, acetonitrile and water). So we further focus on discussing the N atom position and solvent effects on the energy level and Soret/Q bands of FBP, NCP and NECP, as well as clarifying its variation regularity and mechanism.

[Spectroscopic studies of guanidine hydrochloride-induced unfolding of hemoglobin].

In the present paper, based on the ultraviolet-visible (UV-Vis) absorption spectroscopy, fluorescence spectroscopy, and stopped flow-fluorescence spectroscopy, the authors studied the protein unfolding process of hemoglobin induced by GdmHcl. The experiments result shows that there were two different procedures about GdmHcl inducing hemoglobin unfolding from the evidences of UV-Vis absorption spectrum and fluorescence phase diagrams. Namely, the hemoglobin subunit exhibits depolymerization, forming the intermediates when incubated with GdmHcl at the concentration of 1. 0 mol x L(-1). With the increase in the concentration, various subunit structure became loose gradually, and the protoheme collapsed eventually. UV-Vis absorption spectroscopy indicates that the addition of reductant can cooperate with the depolymerization of hemoglobin subunit and the disaggregation of protoheme. The reductant results in the unfolding procedure that hemoglobin from "three-state model" turns into "two-state model".

[Comparison between myoglobin and its mutant(D60K) interacting with hydrogen peroxide by spectrum].

To characterize the roles played by surface-charged residue Asp60 in the structure stability of myoglobin when it was replaced with Lys, the interaction of myoglobin[Mb(WT)] and its mutant[Mb(D60K)] with hydrogen peroxide (H2O2) were studied by the method of ultraviolet-visible (UV-Vis) absorption spectroscopy, fluorescence spectroscopy and stopped-flow fluorescence spectroscopy under simulative physiological conditions. There are remarkable differences between Mb(D60K) and Mb (WT) in the UV-Vis absorption spectroscopy and fluorescence spectroscopy of iron porphyrin during the process of interaction. Although we only altered one external amino acide, the data showed that the function and structure stability of Mb(D60K) was greatly changed. Furthermore, results from synchronous fluorescence spectroscopy and stopped-flow fluorescence spectroscopy all indicated that H2O2 had less effect on the structure of Mb(D60K) while the structure of Mb(WT) was notably changed. From a comprehensive and comparative data analysis, the authors determined that the structure of Mb(D60K) was improved when it interacted with H2O2.