Distal Hydrophobic Loop Modulates the Copper Active Site and Reaction of AA13 Polysaccharide Monooxygenases.

Polysaccharide monooxygenases (PMOs) use a type-2 copper center to activate O2 for the selective hydroxylation of one of the two C-H bonds of glycosidic linkages. Our electron paramagnetic resonance (EPR) analysis and molecular dynamics (MD) simulations suggest the unprecedented dynamic roles of the loop containing the residue G89 (G89 loop) on the active site structure and reaction cycle of starch-active PMOs (AA13 PMOs). In the Cu(II) state, the G89 loop could switch between an "open" and "closed" conformation, which is associated with the binding and dissociation of an aqueous ligand in the distal site, respectively. The conformation of the G89 loop influences the positioning of the copper center on the preferred substrate of AA13 PMOs. The dissociation of the distal ligand results in the bending of the T-shaped core of the Cu(II) active site, which could help facilitate its reduction to the active Cu(I) state. In the Cu(I) state, the G89 loop is in the "closed" conformation with a confined copper center, which could allow for efficient O2 binding. In addition, the G89 loop remains in the "closed" conformation in the Cu(II)-superoxo intermediate, which could prevent off-pathway superoxide release via exchange with the distal aqueous ligand. Finally, at the end of the reaction cycle, aqueous ligand binding to the distal site could switch the G89 loop to the "open" conformation and facilitate product release.

Insights on microbial fuel cells for sustainable biological nitrogen removal from wastewater: A review.

Microbial fuel cells (MFCs) have emerged as a promising technology for energy-efficient wastewater treatment. The feasibility of integrating biological nitrogen removal into MFC systems has been reported. However, better pollutant removal efficiency and power production need to be achieved at a lower cost for a sustainable wastewater treatment system. The objective of this paper is to critically review the nitrogen removal process in various MFC configurations, factors that influence this process, and challenges that should be overcome in future studies. Based on the results of the review, shortcut nitrification-autotrophic denitrification in an MFC is an option as it minimizes the aeration energy and C/N ratio requirement; however, it is necessary to evaluate the N2O emission further. Another attractive option is the heterotrophic anodic denitrification process as it demonstrates the potential for free-buffer MFCs, but the nitrogen removal efficiency at low C/N ratios needs improvement. Bacteria population in MFC system also plays an essential role in both contaminant removal and electricity generation. It can be concluded that MFCs can be a low cost, sustainable solution for the treatment of wastewater and removal of nitrogen. Moreover, selection of MFC configuration will depend on the nature of the wastewater.

Lindermyrrhin, a novel 3,4-dihydroisocoumarin from Lindera myrrha roots.

A novel 3,4-dihydroisocoumarin, lindermyrrhin (1), along with three known compounds, quercetin (2), northalifoline (3) and N-formyl-laurolitsine (4) were isolated from the roots of Lindera myrrha. The structure of compound 1 was identified by interpretation of their spectroscopic data as well as comparison with those reported in the literature. The novel compound 1 represents the first 3,4-dihydroisocoumarin bearing a 2-hydroxyisopropyl substituent at C-3.

Biodegradation of natural rubber and deproteinized natural rubber by enrichment bacterial consortia.

This study examined the biodegradation of natural rubber (NR) and deproteinized natural rubber (DPNR) by bacterial consortia enriched from a rubber-processing factory's waste in Vietnam. The results reveal the degradation in both NR and DPNR, and the DPNR was degraded easier than NR. The highest weight loss of 48.37% was obtained in the fourth enrichment consortium with DPNR, while 35.39% was obtained in the fifth enrichment consortium with NR after 14 days of incubation. Nitrogen content and fatty acid content determined by Kjeldahl method and fourier transform infrared spectroscopy (FTIR), respectively, were decreased significantly after being incubated with the consortia. Structure of degraded rubber film analyzed by nuclear magnetic resonance spectroscopy showed the presence of aldehyde group, a sign of rubber degradation. Bacterial cells tightly adhering and embedding into NR and DPNR films were observed by scanning electron microscopy. There were differences in the bacterial composition of the consortia with NR and DPNR, which were determined by metagenomic analysis using 16S rRNA gene sequencing. The phyla Bacteroidetes and Proteobacteria may play a role in the degradation of non-isoprene compounds such as protein or lipid, while the phylum Actinobacteria plays a crucial role in the degradation of rubber hydrocarbon in all consortia.

Atypical Lindenane-Type Sesquiterpenes from Lindera myrrha.

Two new lindenane sesquiterpenes were obtained from the roots of Lindera myrrha. These compounds were structurally elucidated by HRMS data, extensive NMR analyses, and comparison between experimental and theoretical 13C-NMR data. Myrrhalindenane A is the first monomeric seco-d lindenane displaying a non-rearranged, cyclohexanic C-ring. Myrrhalindenane B is the second occurrence of an angular lindenane-sesquiterpene related to a C6-C7 lactonization.

In vitro model reveals a role for mechanical stretch in the remodeling response of lymphatic muscle cells.

OBJECTIVE: Using primary LMCs in vitro, we sought to characterize the impact of LMC remodeling on their functional and molecular response to mechanical loading and culture conditions. METHODS: Primary "wounded leg" LMCs were derived from the hindlimb of three sheep who underwent lymphatic injury 6 weeks prior, while "control leg" LMCs were derived from the contralateral, unwounded, limb. Function of the LMCs was characterized in response to media of variable levels of serum (10% vs 0.2%) and glucose (4.5 vs 1 g/L). Functional and proteomic data were evaluated in LMCs exposed to cyclic stretch (0.1 Hz, 7.5% elongation) for 1 week. RESULTS: LMCs were sensitive to changes in serum levels, significantly reducing overall activity and collagen synthesis under low serum conditions. LMCs from the remodeled vessel had higher baseline levels of metabolic activity but not collagen synthesis. Cyclic loading induced cellular alignment perpendicular to the axis of stretch and alterations in signaling pathways associated with metabolism. Remodeled LMCs had consistently higher levels of metabolic activity and were more resistant to strain-induced apoptosis. CONCLUSIONS: LMCs exist on a functional spectrum, becoming more active in response to stretching and maintaining phenotypic remodeling in response to local lymphatic/tissue damage.

Interaction of carbohydrate binding module 20 with starch substrates.

CBM20s are starch-binding domains found in many amylolytic enzymes, including glucoamylase, alpha-amylase, beta-amylases, and a new family of starch-active polysaccharide monooxygenases (AA13 PMOs). Previous studies of CBM20-substrate interaction only concerned relatively small or soluble amylose molecules, while amylolytic enzymes often work on extended chains of insoluble starch molecules. In this study, we utilized molecular simulation techniques to gain further insights into the interaction of CBM20 with substrates of various sizes via its two separate binding sites, termed as BdS1 and BdS2. Results show that substrate binding at BdS1 involving two conserved tryptophan residues is about 2-4 kcal mol-1 stronger than that at BdS2. CBM20 exhibits about two-fold higher affinity for helical substrates than for the amylose random coils. The affinity for amylose individual double helices does not depend on the helices' length. At least three parallel double helices are required for optimal binding. The binding affinity for a substrate containing 3 or more double helices is ∼-15 kcal mol-1, which is 2-3 kcal mol-1 larger than that for individual double helices. 100 ns molecular dynamics simulations were carried out for the binding of CBM20 to an extended substrate containing 3 layers of 9 60-unit double helices (A3L). A stable conformation of CBM20-A3L was found at BdS1. However, when CBM20 binds A3L viaBdS2, it moves across the surface of the substrate and does not form a stable complex. MD simulations show that small amylose helices are quickly disrupted upon binding to CBM20. Our results provide some important molecular insights into the interactions of CBM20 with starch substrates, which will serve as the basis for further studies of CBM20-containing enzymes, including AA13 PMOs.

Adaptive filtering of physiological noises in fNIRS data.

The study presents a recursive least-squares estimation method with an exponential forgetting factor for noise removal in functional near-infrared spectroscopy data and extraction of hemodynamic responses (HRs) from the measured data. The HR is modeled as a linear regression form in which the expected HR, the first and second derivatives of the expected HR, a short-separation measurement data, three physiological noises, and the baseline drift are included as components in the regression vector. The proposed method is applied to left-motor-cortex experiments on the right thumb and little finger movements in five healthy male participants. The algorithm is evaluated with respect to its performance improvement in terms of contrast-to-noise ratio in comparison with Kalman filter, low-pass filtering, and independent component method. The experimental results show that the proposed model achieves reductions of 77% and 99% in terms of the number of channels exhibiting higher contrast-to-noise ratios in oxy-hemoglobin and deoxy-hemoglobin, respectively. The approach is robust in obtaining consistent HR data. The proposed method is applied for both offline and online noise removal.

HIV Knowledge, Risk Behavior, Stigma, and Their Impact on HIV Testing among Asian American and Pacific Islanders: A Review of Literature.

Asian American and Pacific Islanders (AAPIs) are the fastest growing population in the United States with documented increases in HIV rates. AAPIs are as likely as other racial/ethnic groups to engage in HIV-related risk behaviors, while being concomitantly less likely to have been HIV tested. Testing is a critical step in HIV prevention. Research points to various barriers to HIV-related testing including HIV knowledge and attitude and stigma. However, these factors and their impact among AAPIs are poorly understood. Myths about this population's "model minority" status compound AAPIs' sociocultural factors including English language proficiency, access to healthcare, and a culture of "silence" that negatively influences HIV-related research. In this article, the authors review the scientific literature on knowledge, risk behavior, and stigma to document the current state of research. Based on the review the authors offer a set of research, policy, and practice recommendations for social workers and other service providers working with AAPIs.

Bundled-Optode Method in Functional Near-Infrared Spectroscopy.

In this paper, a theory for detection of the absolute concentrations of oxy-hemoglobin (HbO) and deoxy-hemoglobin (HbR) from hemodynamic responses using a bundled-optode configuration in functional near-infrared spectroscopy (fNIRS) is proposed. The proposed method is then applied to the identification of two fingers (i.e., little and thumb) during their flexion and extension. This experiment involves a continuous-wave-type dual-wavelength (760 and 830 nm) fNIRS and five healthy male subjects. The active brain locations of two finger movements are identified based on the analysis of the t- and p-values of the averaged HbOs, which are quite distinctive. Our experimental results, furthermore, revealed that the hemodynamic responses of two-finger movements are different: The mean, peak, and time-to-peak of little finger movements are higher than those of thumb movements. It is noteworthy that the developed method can be extended to 3-dimensional fNIRS imaging.

Bundled-optode implementation for 3D imaging in functional near-infrared spectroscopy.

The paper presents a functional near-infrared spectroscopy (fNIRS)-based bundled-optode method for detection of the changes of oxy-hemoglobin (HbO) and deoxy-hemoglobin (HbR) concentrations. fNIRS with 32 optodes is utilized to measure five healthy male subjects' brain-hemodynamic responses to arithmetic tasks. Specifically, the coordinates of 256 voxels in the three-dimensional (3D) volume are computed according to the known probe geometry. The mean path length factor in the Beer-Lambert equation is estimated as a function of the emitter-detector distance, which is utilized for computation of the absorption coefficient. The mean values of HbO and HbR obtained from the absorption coefficient are then applied for construction of a 3D fNIRS image. Our results show that the proposed method, as compared with the conventional approach, can detect brain activity with higher spatial resolution. This method can be extended for 3D fNIRS imaging in real-time applications.

State-space models of impulse hemodynamic responses over motor, somatosensory, and visual cortices.

THE PAPER PRESENTS STATE SPACE MODELS OF THE HEMODYNAMIC RESPONSE (HR) OF FNIRS TO AN IMPULSE STIMULUS IN THREE BRAIN REGIONS: motor cortex (MC), somatosensory cortex (SC), and visual cortex (VC). Nineteen healthy subjects were examined. For each cortex, three impulse HRs experimentally obtained were averaged. The averaged signal was converted to a state space equation by using the subspace method. The activation peak and the undershoot peak of the oxy-hemoglobin (HbO) in MC are noticeably higher than those in SC and VC. The time-to-peaks of the HbO in three brain regions are almost the same (about 6.76 76 ± 0.2 s). The time to undershoot peak in VC is the largest among three. The HbO decreases in the early stage (~0.46 s) in MC and VC, but it is not so in SC. These findings were well described with the developed state space equations. Another advantage of the proposed method is its easy applicability in generating the expected HR to arbitrary stimuli in an online (or real-time) imaging. Experimental results are demonstrated.

Toward 100 Mega-frames per second: design of an ultimate ultra-high-speed image sensor.

Our experience in the design of an ultra-high speed image sensor targeting the theoretical maximum frame rate is summarized. The imager is the backside illuminated in situ storage image sensor (BSI ISIS). It is confirmed that the critical factor limiting the highest frame rate is the signal electron transit time from the generation layer at the back side of each pixel to the input gate to the in situ storage area on the front side. The theoretical maximum frame rate is estimated at 100 Mega-frames per second (Mfps) by transient simulation study. The sensor has a spatial resolution of 140,800 pixels with 126 linear storage elements installed in each pixel. The very high sensitivity is ensured by application of backside illumination technology and cooling. The ultra-high frame rate is achieved by the in situ storage image sensor (ISIS) structure on the front side. In this paper, we summarize technologies developed to achieve the theoretical maximum frame rate, including: (1) a special p-well design by triple injections to generate a smooth electric field backside towards the collection gate on the front side, resulting in much shorter electron transit time; (2) design technique to reduce RC delay by employing an extra metal layer exclusively to electrodes responsible for ultra-high speed image capturing; (3) a CCD specific complementary on-chip inductance minimization technique with a couple of stacked differential bus lines.

Electrochemical properties of poly(3,4-ethylenedioxythiophene) nanofiber non-woven web formed by electrospinning.

Electrically conducting nano (micro) poly(3,4-ethylenedioxythiophene) (PEDOT) fiber non-woven web was fabricated using the electrospinning technique by applying high voltage of 10 to 30 kV to the electrospinning solution. To investigate the effects of various conditions on formation and properties of PEDOT fiber non-woven web, we changed the solvent or other components and their concentrations. We used 1-propanol or 1-butanol as a solvent and poly(vinyl pyrrolidone) (PVP) as a matrix polymer to prepare the electrospinning solution. The electrical conductivity of the electro-spun PEDOT non-woven web was as high as 7.5 S/cm when 1-propanol was used as the solvent. Electrochemical capacitor was assembled using one pair of the PEDOT non-woven webs as the electrodes by a simple stack method, where metal plates were used as current collectors. We observed the electrochemical charge and discharge behavior of the capacitor, confirming that the PEDOT non-woven web can be used as the electrode for flexible electrochemical capacitor.