Effects of Cations and PH on Antimicrobial Activity of Thanatin and s-Thanatin against _Escherichia coli_ ATCC25922 and _B. subtilis_ ATCC 21332

Thanatin and s-thanatin were insect antimicrobial peptides which have shown potent antimicrobial activities on a variety of microbes. In order to investigate the effect of cations and pH on the activity of these peptides against Gram-negative bacteria and Gram-positive bacteria, the antimicrobial activities of both peptides were studied in increasing concentrations of monovalent cations (K^+^ and Na^+^), divalent cations (Ca^2+^ and Mg^2+^) and H^+^. The NCCLS broth microdilution method showed that both peptides were sensitive to the presence of cations. The divalent cations showed more antagonized effect on the activity against Gram-negative bacteria than the monovalent cations, since the two peptides lost the ability to inhibit bacterial growth at a very low concentration. In addition, the activities of both peptides tested were not significantly affected by pH. Comparing to studies of other antibacterial peptide activities, our data support a hypothesis that positive ions affect the sensitivity to cation peptides

UV-triggered dopamine polymerization: Control of polymerization, surface coating, and photopatterning

UV irradiation is demonstrated to initiate dopamine polymerization and deposition on different surfaces under both acidic and basic pH. The observed acceleration of the dopamine polymerization is explained by the UV-induced formation of reactive oxygen species that trigger dopamine polymerization. The UV-induced dopamine polymerization leads to a better control over polydopamine deposition and formation of functional polydopamine micropatterns

Microfluidic Fabrication of Colloidal Nanomaterials-Encapsulated Microcapsules for Biomolecular Sensing

Implantable sensors that detect biomarkers in vivo are critical for early disease diagnostics. Although many colloidal nanomaterials have been developed into optical sensors to detect biomolecules in vitro, their application in vivo as implantable sensors is hindered by potential migration or clearance from the implantation site. One potential solution is incorporating colloidal nanosensors in hydrogel scaffold prior to implantation. However, direct contact between the nanosensors and hydrogel matrix has the potential to disrupt sensor performance. Here, we develop a hollow-microcapsule-based sensing platform that protects colloidal nanosensors from direct contact with hydrogel matrix. Using microfluidics, colloidal nanosensors were encapsulated in polyethylene glycol microcapsules with liquid cores. The microcapsules selectively trap the nanosensors within the core while allowing free diffusion of smaller molecules such as glucose and heparin. Glucose-responsive quantum dots or gold nanorods or heparin-responsive gold nanorods were each encapsulated. Microcapsules loaded with these sensors showed responsive optical signals in the presence of target biomolecules (glucose or heparin). Furthermore, these microcapsules can be immobilized into biocompatible hydrogel as implantable devices for biomolecular sensing. This technique offers new opportunities to extend the utility of colloidal nanosensors from solution-based detection to implantable device-based detection. Keywords: biomolecular sensing; Microcapsules; microfluidic fabrication; nanosensorsJuvenile Diabetes Research Foundation International (Award 17-2013-507

First-principle study on the electronic structure and optical property of new diluted magnetic semiconductor (Y0.75Sr0.25) (Cu0.75Mn0.25)SO

In this research, we investigated the electronic structure and optical property of new diluted magnetic semiconductor (Y0.75Sr0.25) (Cu0.75Mn0.25)SO with decoupled charge and spin doping by first-principle calculation. We also compared (Y0.75Sr0.25) (Cu0.75Mn0.25)SO with pure YCuSO, and found that (Y0.75Sr0.25) (Cu0.75Mn0.25)SO is still a direct semiconductor with a band gap 1.20eV. The important difference from YCuSO is that the DOS of (Y0.75Sr0.25) (Cu0.75Mn0.25)SO presents asymmetry around fermi surface, leading to obvious spin order and ferror-magnetism due to the p-d hybridization through Mn 3d and S 3p. In case of the optical properties (including reflectivity coefficient, absorption coefficient, the imaginary part and real part of complex dielectric constant), the intensity of all peaks for both pure and doped YCuSO tends to zero above 15.5eV. However, the value of all the peaks for (Y0.75Sr0.25) (Cu0.75Mn0.25)SO reduces to some extent due to the Sr and Mn dopant. In addition, the position of all the peaks for (Y0.75Sr0.25) (Cu0.75Mn0.25)SO have a “red shift”, probably originating from the impurity states generated by the p-d hybridization through Mn 3d and S 3p. This will be beneficial for searching new 1111 phase DMS

Induction of Viable but Nonculturable State in Rhodococcus and Transcriptome Analysis Using RNA-seq.

Viable but nonculturable (VBNC) bacteria, which maintain the viability with loss of culturability, universally exist in contaminated and non-contaminated environments. In this study, two strains, Rhodococcus sp. TG13 and TN3, which were isolated from PCB-contaminated sediment and non-contaminated sediment respectively, were investigated under low temperature and oligotrophic conditions. The results indicated that the two strains TG13 and TN3 could enter into the VBNC state with different incubation times, and could recover culturability by reversal of unfavourable factors and addition of resuscitation-promoting factor (Rpf), respectively. Furthermore, the gene expression variations in the VBNC response were clarified by Illumina high throughput RNA-sequencing. Genome-wide transcriptional analysis demonstrated that up-regulated genes in the VBNC cells of the strain TG13 related to protein modification, ATP accumulation and RNA polymerase, while all differentially expressed genes (DEGs) in the VBNC cells of the strain TN3 were down-regulated. However, the down-regulated genes in both the two strains mainly encoded NADH dehydrogenase subunit, catalase, oxidoreductase, which further verified that cold-induced loss of ability to defend oxidative stress may play an important role in induction of the VBNC state. This study further verified that the molecular mechanisms underlying the VBNC state varied with various bacterial species. Study on the VBNC state of non-pathogenic bacteria will provide new insights into the limitation of environmental micro-bioremediation and the cultivation of unculturable species

Stability and Elasticity of Quasi Hexagonal Fullerene Monolayer from First Principles Study

As a newly synthesized two dimensional carbon material, the stability study of monolayer fullerene networks or quasi hexagonal phase fullerenes (qhp C 60) is timely desirable. We have investigated the stabilities of qhp C 60, including thermal, structural, mechanical, and thermodynamic stabilities, as well as the bonding characteristics, ductility, and mechanical properties, via first principles calculations. The results show that qhp C 60 is energetically, mechanically, and thermodynamically stable. The thermodynamic stability of qhp C 60 at 300 K and 600 K is verified. The bonding characteristics of qhp C 60 are analyzed from the bond length, and it has sp(2) and sp(3) hybridization. The Pugh ratio (B/G) and Poisson's ratio (v) indicate similar ductility with graphite and graphene. We also found that qhp C 60 has the lowest hardness and the anisotropy of the material. In addition, the electronic characteristics, including electron localization function (ELF), crystal orbital Hamiltonian population (COHP), and density of states (DOS) at different temperatures, are analyzed to verify the thermal stability of the material. Our results might be helpful in the material design of qhp C 60 related applications

A Dynamic Study of a Karst Spring Based on Wavelet Analysis and the Mann-Kendall Trend Test

Over the last 40 years, declining spring water flow rates have become a typical feature of karst springs in Northern China. Wavelet analysis, the Mann-Kendall trend test and the mutation test were used to analyze dynamic monitoring data of groundwater levels and atmospheric precipitation in the Jinan karst spring area, from 1956 to 2013, to study hydrological responses to atmospheric precipitation over one-year periods. Results from this analysis show that: (1) Atmospheric precipitation and the spring water level displayed multi-scale change characteristics, having two very similar cycles of change of 16 and 12 years. This finding shows that atmospheric precipitation generates a direct impact on the level of spring water. (2) From 1956 to 2013, the groundwater level in the Jinan spring area had a significant downward trend (0.65 m/10a). Precipitation recorded an increasing trend (12.65 mm/10a), however this was not significant. The weight of the influencing factors of the spring dynamic therefore changed due to the influence of human factors. (3) A mutation of atmospheric precipitation occurred in 1999, after which annual precipitation increased. Results for the mutation of the groundwater level showed an initial change in 1967. After this change the water level continued to decrease before rapidly increasing after 2004. The future trend of the spring water level should be maintained with consistent precipitation (having an upward trend), indicating that atmospheric precipitation is not the only factor affecting the dynamics of the spring. (4) Different periods were identified on the multiple regression model. The main influencing factors on groundwater level over the past 58 years were identified as a transition from precipitation to artificial mining. These results also validate the suitability and reliability of using wavelet analysis and the Mann-Kendall test method to study groundwater dynamics; these results provide a reference for the future protection of the Jinan City spring