Halogenol- versus alkanol-induced structural transitions of acid-denatured glucoamylase: Characterization of alcohol-induced states

Different probes such as far- and near-UV CD spectral signals, ANS binding, Trp fluorescence and three-dimensional fluorescence were used to study halogenol- versus alkanol-induced conformational transitions in the acid-denatured state (pH 1.0) of Aspergillus niger glucoamylase (GA). These alcohols showed significant retrieval of the protein structure, inducing both secondary and tertiary structural changes, as evident from the increase in the α-helix and decrease in ANS binding, respectively. However, halogenols were found more competent than alkanols, requiring lesser alcohol concentration to induce similar spectral change. The effectiveness of these alcohols showed the order: HFIP > TFE > 2-chloroethanol for halogenols while tert-butanol > 1-propanol > 2-propanol > ethanol > methanol for alkanols. Both Trp fluorescence and near-UV CD spectra showed anomalous pattern, though the order of effectiveness remained the same as found with far-UV CD spectra and ANS fluorescence. Three-dimensional fluorescence results of the acid-denatured state (pH 1.0) of GA in the presence of 5.5 M tert-butanol agreed well with the data obtained from far-UV CD and Trp fluorescence. All these results suggested the formation of partially folded states of GA obtained in the presence of these alcohols, being more effective with halogenols than alkanols.     

Photobiomodulation of human adipose-derived stem cells using 810 nm and 980 nm lasers operates via different mechanisms of action

Photobiomodulation (PBM) using red or near-infrared (NIR) light has been used to stimulate the proliferation and differentiation of adipose-derived stem cells. The use of NIR wavelengths such as 810 nm is reasonably well accepted to stimulate mitochondrial activity and ATP production via absorption of photons by cytochrome c oxidase. However, the mechanism of action of 980 nm is less well understood. Here we study the effects of both wavelengths (810 nm and 980 nm) on adipose-derived stem cells in vitro. Both wavelengths showed a biphasic dose response, but 810 nm had a peak dose response at 3 J/cm² for stimulation of proliferation at 24 h, while the peak dose for 980 nm was 10–100 times lower at 0.03 or 0.3 J/cm². Moreover, 980 nm (but not 810 nm) increased cytosolic calcium while decreasing mitochondrial calcium. The effects of 980 nm could be blocked by calcium channel blockers (capsazepine for TRPV1 and SKF96365 for TRPC channels), which had no effect on 810 nm. To test the hypothesis that the chromophore for 980 nm was intracellular water, which could possibly form a microscopic temperature gradient upon laser irradiation, we added cold medium (4 °C) during the light exposure, or pre-incubated the cells at 42 °C, both of which abrogated the effect of 980 nm but not 810 nm. We conclude that 980 nm affects temperature-gated calcium ion channels, while 810 nm largely affects mitochondrial cytochrome c oxidase.     

Simple liquid chromatography method for the quantification of irinotecan and SN38 in sheep plasma: Application to in vivo pharmacokinetics after pulmonary artery chemoembolization using drug eluting beads

A rapid and simple liquid chromatography–fluorescence detection (LC–FD) method was developed and validated for the simultaneous quantification of irinotecan (CPT11) and SN38 in sheep plasma. Camptothecin (CPT) was used as the internal standard. A single step protein precipitation with acetonitrile was used for sample preparation. The separation was achieved using a 5 μm C18 column (250 mm × 4.5 mm, 5 μm) with a mobile phase composed of 36 mM sodium dihydrogen phosphate dehydrate and 4 mM sodium 1 heptane sulfonate–acetonitrile (72:28), the pH of the mobile phase was adjusted to 3. The flow rate was 1.45 mL/min and the fluorescence detection was operated at 355/515 nm (excitation/emission wavelengths). The run time was 13 min. The method was validated with respect to selectivity, extraction recovery, linearity, intra- and inter-day precision and accuracy, limit of quantification and stability. The method has a limit of quantification of 5 ng/mL for both CPT11 and SN38. The assay was linear over concentrations ranging from 5 to 5000 ng/mL and to 240 ng/mL for CPT11 and SN38, respectively. This method was used successfully to perform plasma pharmacokinetic studies of CPT11 after pulmonary artery embolization (PACE) in a sheep model. It was also validated for CPT11 and SN38 analysis in sheep lymph and human plasma.     

Molecular analysis of the bacterial community in digestive tract of rabbit

This work aimed to study the stability over time of the bacterial community in cæcum and fæces of the rabbit (diversity index and structure) without experimental disturbance and to evaluate its relationships with environmental parameters. Soft and hard fæces of 14 rabbits were sampled for 5 weeks while cæcal content was sampled on the 3rd week (by surgery) and the 5th week (at slaughter). Bacterial communities were assessed by studying CE-SSCP profiles of 16S rRNA genes fragments. Redox potential, pH, NH3-N concentration and volatile fatty acid concentrations were measured in the cæcum. Data showed that bacterial communities of soft and hard fæces barely differed from that of the cæcum (ANOSIM-R < 0.25; p < 0.05). Without disturbance, the bacterial communities of fæces were stable over time (ANOSIM-R < 0.25; p < 0.001). However, the bacterial communities of cæcum and fæces were affected by the surgery (ANOSIM-R = 0.22–0.33; p < 0.001). The cæcal content was an acidic (pH = 6.03 ± 0.33) and an anaerobic environment (redox potential = ?160 ± 43 mV). Only the redox potential was correlated with the diversity index of the bacterial community of the cæcum (R² = 0.35; p < 0.05) and no environmental parameters were correlated to its structure.     

Complete separation of urinary metabolites of xylene in HPLC/DAD using β-cyclodextrin: Application for biological monitoring

To determine the biomarkers of exposure to xylene, urinary 2-, 3- and 4-methyl-hippuric acids, a new HPLC/DAD analytical method has been developed, which uses β-cyclodextrin as an additive for elution; its complexing abilities are exploited to achieve complete chromatographic separation of the three isomers. The mobile phase was a 3% aqueous solution of β-cyclodextrin, pH 3, and methanol, 80:20, in isocratic conditions, with a flow rate of 1 mL/min. To optimize quantitative analysis three wavelengths were employed for detection: λ = 198 nm, λ = 200 nm, and λ = 202 nm. SPE was applied for the extraction from urine samples of analytes. Validation parameters show recoveries always above 82%; LOD was set at 1 μg/mL with an LOQ of 3 μg/mL. The linear dynamic range (from 4 to 100 μg/mL) showed excellent correspondence. This method is rapid and inexpensive and can be applied to several samples simultaneously using a manifold for SPE extraction. The analytes were separated completely and could be fully quantified. The method was used for the analysis of urine samples from 54 workers exposed to xylene in hospital laboratories and showed a good applicability while allowing quantification even at low doses.     

Design,synthesis and activity evaluation of novel peptide fusion inhibitors targeting HIV-1 gp41

Human immunodeficiency virus type 1 (HIV-1), the pathogen of acquired immunodeficiency syndrome (AIDS), causes about 2 million people to death every year. Fusion inhibitors targeted the envelope protein (gp41) represent a novel and alternative approach for anti-AIDS therapy, which terminates the HIV-1 life cycle at an early stage. Using CP621-652 as a template, a series of peptides were designed, synthesized and evaluated in vitro assays. An interesting phenomenon was found that the substitution of hydrophobic residues at solvent accessible sites could increase the anti-HIV activity when the C-terminal sequence was extended with an enough numbers of amino acids. After the active peptides was synthesized and evaluated, peptide 8 showed the best anti-HIV-1 IIIB whole cell activity (MAGI IC₅₀ = 53.02 nM). Further study indicated that peptide 8 bound with the gp41 NHR helix, and then blocked the conformation of 6-helix, thus inhibited virus–cell membrane fusion. The results would be helpful for the design of peptide fusion inhibitors against HIV-1 infection.     

Effect of microwave irradiation on the structure of glucoamylase

In the present study, we describe changes in the primary and secondary structural patterns of glucoamylase during starch hydrolysis under microwave irradiation using SDS-PAGE and circular dichroism (CD) spectroscopy. Our SDS-PAGE results show that the primary structure of glucoamylase did not change after microwave irradiation. According to the CD spectra, the positive peak height (λ = 193 nm) of the microwave-irradiated samples decreased by 36.4–68.2% compared to those without irradiation, whereas the double negative peak height (λ = 206 nm, λ = 220 nm) increased by 10.8–31.4%. In addition, the positive peak (λ = 193 nm) shifted by 0.2–3 nm. After treatment of glucoamylase with microwave irradiation, the α-helical content of glucoamylase decreased sharply, whereas the β-sheet, β-turn and random coil content increased gradually. The conformational changes of glucoamylase after microwave irradiation provide theoretical support for the mechanism whereby microwave irradiation accelerates starch hydrolysis catalyzed by glucoamylase.     

Analysis of the relationship between the spectral characteristics of maize canopy and leaf area index under drought stress

Maize is one of the most widespread grain crops in the world; however, more than 70% of corn in China suffers some degree of drought disaster every year. Leaf area index (LAI) is an important biophysical parameter of the vegetation canopy and has important significance for crop yield estimation. Using the data of canopy spectral reflectance and leaf area index (LAI) for maize plants experiencing different levels of soil moisture from 2011 to 2012, the characteristics of the canopy reflective spectrum and its first derivative, and their relationships to leaf area index, were analyzed. Soil moisture of the control group was about 75% while that of the drought stress treatment was about 45%. In addition, LAI retrieval models for maize were established using vegetation indices (VIs) and principal component analysis (PCA) and the models were tested using independent datasets representing different soil water contents and different developmental stages of maize. The results showed that canopy spectral reflectances were in accordance with the characteristics of green plants, under both drought stress and at different developmental stages. In the visible band, canopy reflectance for both healthy and damaged vegetation had a green-wavelength peak and a red-wavelength valley; reflectance under drought stress, especially in the green peak (about 550 nm) and the red valley (about 676 nm) was higher than in the control group. In the near-infrared band, the canopy spectral reflectance decreased substantially between 780 and 1350 nm under drought stress. Moreover, the red edge of the spectrum was shifted toward blue wavelengths. The first derivative spectrum showed a double peak phenomenon at the edge of the red band at different developmental stages: the main peak appeared between 728 and 732 nm and the minor peak at about 718 nm. The double peaks become more obvious through the growth and development of the maize, with the most notable effect during the silking and milk stages, after which it gradually decreased. During maize growth, the LAI of all plants, regardless of soil moisture conditions, increased, and the largest LAI also occurred during the silking and milk stages. During those stages, the LAI of plants under different drought stress levels was significantly lower (by 20% or more) than in normal plants with sufficient water supplies. The LAI was highly significantly correlated with canopy spectral reflectance in the bands from 350 nm to 510 nm, from 571 nm to 716 nm, and from 1450 nm to 1575 nm. Also, the LAI was significantly correlated with red edge parameters and several VIs. The Perpendicular Vegetation Index (PVI) had the best correlation with LAI, with a coefficient of determination (R²) of 0.726 for the exponential correlation. Using dependent data, a LAI monitoring model for the maize canopy was constructed using PCA and VI methods. The test results showed that both the VI and PCA methods of monitoring maize LAI could provide robust estimates, with the predicted values of LAI being significantly correlated with the measured values. The model based on PVI showed higher precision under the drought stresses, with a correlation coefficient of 0.893 (n = 27), while the model based on PCA was more precise under conditions of adequate soil moisture, with a correlation coefficient of 0.877 (n = 32). Therefore, a synthesis of the models based on both VI and PCA could be more reliable for precisely predicting LAI under different levels of drought stresses in maize.     

Efficient light absorbers based on thiophene-fused boron dipyrromethene (BODIPY) dyes

We present the development of the thiophene-fused boron dipyrromethene derivatives as efficient light absorbers. The two strategies for the evolution of the optical properties such as the peak positions of absorption wavelengths and molar extinct coefficients were established by the substituent effects: by introducing iodine groups, the bathochromic shifts of the peak positions (+15 nm) and the enhancement of molar extinct coefficients were simultaneously received owing to the heavy atom effect. Next, it was found that the modification with the trifluoromethyl group contributed to the large bathochromic shift (+60 nm) because of the lowering effect on the lowest unoccupied molecular orbital of the dye by the substituent. Finally, we obtained the dyes with large molar extinct coefficients (184,140 M^?1 cm^?1 at 592 nm, 72,180 M^?1 cm^?1 at 623 nm), sharp absorption bands, and low emissions.     

Optimization of Zn2+-containing mobile phase for simultaneous determination of kynurenine,kynurenic acid and tryptophan in human plasma by high performance liquid chromatography

In the present work we have developed a standard-addition HPLC method using a mobile phase containing low concentration of ZnAc₂ to determine physiological level of kynurenine (KYN), kynurenic acid (KYNA) and tryptophan (TRP) in human plasma simultaneously. The method greatly improved the sensitivity of KYNA, the resolution of KYNA and TRP, and avoided clotting risk caused by high concentration of ZnAc₂ in mobile phase. Samples were deproteinized by addition of equal volume of 0.6 mol/L HClO₄. Analytes in supernatants were separated by an Agilent HC-C18 (2) analytical column; an aqueous mobile phase containing 20 mmol/L NaAc, 3 mmol/L ZnAc₂ and 7% acetonitrile at flow rate of 1.0 mL/min. Detections were performed by a variable wavelength detector at wavelength 365 nm for KYN and a fluorescence detector at wavelengths excitation 344 nm and emission 398 nm for KYNA and TRP. Good linear responses were found with r² > 0.999 for all analytes within the concentration range of physiological levels. The limit of detection of the developed method was 0.03 μmol/L, 0.9 nmol/L and 0.4 μmol/L for KYN, KYNA and TRP respectively. Recoveries from spiked human plasma were 95.4–99.7% for KYN, 98.9–104% for KYNA and 96.5–100.2% for TRP. All CVs for the repeatability and intermediate precision were less than 5%. We conclude that the developed method is helpful for the research investigations in KYN pathway of TRP metabolism.     

Action spectra of photosystems II and I and quantum yield of photosynthesis in leaves in State 1

The spectral global quantum yield (Y_II, electrons/photons absorbed) of photosystem II (PSII) was measured in sunflower leaves in State 1 using monochromatic light. The global quantum yield of PSI (Y_I) was measured using low-intensity monochromatic light flashes and the associated transmittance change at 810 nm. The 810-nm signal change was calibrated based on the number of electrons generated by PSII during the flash (4 · O₂ evolution) which arrived at the PSI donor side after a delay of 2 ms. The intrinsic quantum yield of PSI (y_I, electrons per photon absorbed by PSI) was measured at 712 nm, where photon absorption by PSII was small. The results were used to resolve the individual spectra of the excitation partitioning coefficients between PSI (a_I) and PSII (a_II) in leaves. For comparison, pigment–protein complexes for PSII and PSI were isolated, separated by sucrose density ultracentrifugation, and their optical density was measured. A good correlation was obtained for the spectral excitation partitioning coefficients measured by these different methods. The intrinsic yield of PSI was high (y_I = 0.88), but it absorbed only about 1/3 of quanta; consequently, about 2/3 of quanta were absorbed by PSII, but processed with the low intrinsic yield y_II = 0.63. In PSII, the quantum yield of charge separation was 0.89 as detected by variable fluorescence F_v/F_m, but 29% of separated charges recombined (Laisk A, Eichelmann H and Oja V, Photosynth. Res. 113, 145–155). At wavelengths less than 580 nm about 30% of excitation is absorbed by pigments poorly connected to either photosystem, most likely carotenoids bound in pigment–protein complexes.     

Determination of d-saccharic acid-1,4-lactone from brewed kombucha broth by high-performance capillary electrophoresis

Kombucha is a health tonic. d-Saccharic acid-1,4-lactone (DSL), a component of kombucha, inhibits the activity of glucuronidase, an enzyme indirectly related with cancers. To date, there is no efficient method to determine the content of DSL in kombucha samples. In this paper, we report a rapid and simple method for the separation and determination of DSL in kombucha samples, using the high-performance capillary electrophoresis (HPCE) method with diode array detection (DAD). With optimized conditions, DSL can be separated in a 50 cm length capillary at a separation voltage of 20 kV in 40 mmol/L borax buffer (pH 6.5) containing 30 mmol/L SDS and 15% methanol (v/v). Quantitative evaluation of DSL was determined by ultraviolet absorption at λ = 190 nm. The relationship between the peak areas and the DSL concentrations, in a specified working range with linear response, was determined by first-order polynomial regression over the range 50–1500 μg/mL with a detection limit of 17.5 μg/mL. Our method demonstrated excellent reproducibility and accuracy with relative standard deviations (RSD) of less than 5% DSL content (n = 5). This is the first report to determine DSL by HPCE. We have successfully applied this method to determine DSL in kombucha samples in various fermented conditions.     

The gold nanoparticle size and exposure duration effect on the liver and kidney function of rats: In vivo

Nanoparticles (NPs) offer a great possibility for biomedical application, not only to deliver pharmaceutics, but also to be used as novel diagnostic and therapeutic approaches. Currently, there are no data available regarding to what extent the degree of the toxicity and the accumulation of gold nanoparticles (GNPs) are present in in vivo administration. This study aimed to address the GNP size and exposure duration effect on the liver and kidney function of rats: in vivo.MethodsA total of 30 healthy male Wistar-Kyoto rats of the same age (12 weeks old) and weighing 220–240 g of King Saud University colony were used. Animals were randomly divided into groups, two GNP-treated rat groups and one control group (CG). The 50 μl of 10 and 50 nm GNPs was intraperitoneally administered in rats for exposure duration of 3 days. Then, several biochemical parameters such as aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), alanine transaminase (ALT), alkaline phosphatase (ALP), urea (UREA) and creatinine (CREA) were evaluated.ResultsIn this study, the AST values increased with the administration of 10 and 50 nm GNPs compared with the control. The AST values significantly increased with 10 nm GNPs compared with 50 nm GNPs and control. The GGT and ALT values decreased with the administration of 10 and 50 nm GNPs compared with the control. The GGT and ALT values significantly decreased with 50 nm GNPs compared with 10 nm GNPs and control. The ALP values significantly decreased with the administration of 10 and 50 nm GNPs compared with the control. The decrease in ALP values with 10 nm GNPs was higher than those compared with 50 nm GNPs. In this study, the levels of UREA and CREA values increased in a non significant manner after the administration of 10 and 50 nm GNPs compared with the control.ConclusionsThis study demonstrates that the increase in the enzymes AST and the decrease in ALP are smaller GNPs (10 nm) size-dependent for exposure duration of 3 days; while the decrease in the enzymes GGT and ALT are bigger GNPs (50 nm) size-dependent. The levels of UREA and CREA values indicated no significant changes with the administration of 10 and 50 nm GNPs for exposure duration of 3 days compared with the control. The administration of 10 and 50 nm GNPs for short exposure duration of 3 days induced only significant variations with some liver enzymes while kidney showed no significant variations. This study suggests that synthesis and metabolism of GNPs as well as the protection of the liver will be more important issues for medical applications of gold-based nanomaterials in future.     

The role of tryptophans on the cellular uptake and membrane interaction of arginine-rich cell penetrating peptides

Cell-penetrating peptides (CPP) are able to efficiently transport cargos across cell membranes without being cytotoxic to cells, thus present a great potential in drug delivery and diagnosis. While the role of cationic residues in CPPs has been well studied, that of Trp is still not clear. Herein 7 peptide analogs of RW9 (RRWWRRWRR, an efficient CPP) were synthesized in which Trp were systematically replaced by Phe residues. Quantification of cellular uptake reveals that substitution of Trp by Phe strongly reduces the internalization of all peptides despite the fact that they strongly accumulate in the cell membrane. Cellular internalization and biophysical studies show that not only the number of Trp residues but also their positioning in the helix and the size of the hydrophobic face they form are important for their internalization efficacy, the highest uptake occurring for the analog with 3 Trp residues. Using CD and ATR-FTIR spectroscopy we observe that all peptides became structured in contact with lipids, mainly in α-helix. Intrinsic tryptophan fluorescence studies indicate that all peptides partition in the membrane in about the same manner (Kp ~ 10⁵) and that they are located just below the lipid headgroups (~ 10 Å) with slightly different insertion depths for the different analogs. Plasmon Waveguide Resonance studies reveal a direct correlation between the number of Trp residues and the reversibility of the interaction following membrane washing. Thus a more interfacial location of the CPP renders the interaction with the membrane more adjustable and transitory enhancing its internalization ability.     

Bacterial cell-surface displaying of thermo-tolerant glutamate dehydrogenase and its application in l-glutamate assay

In this paper, glutamate dehydrogenase (Gldh) is reported to efficiently display on Escherichia coli cell surface by using N-terminal region of ice the nucleation protein as an anchoring motif. The presence of Gldh was confirmed by SDS-PAGE and enzyme activity assay. Gldh was detected mainly in the outer membrane fraction, suggesting that the Gldh was displayed on the bacterial cell surface. The optimal temperature and pH for the bacteria cell-surface displayed Gldh (bacteria-Gldh) were 70 °C and 9.0, respectively. Additionally, the fusion protein retained almost 100% of its initial enzymatic activity after 1 month incubation at 4 °C. Transition metal ions could inhibit the enzyme activity to different extents, while common anions had little adverse effect on enzyme activity. Importantly, the displayed Gldh is most specific to l-glutamate reported so far. The bacterial Gldh was enabled to catalyze oxidization of l-glutamate with NADP⁺ as cofactor, and the resultant NADPH can be detected spectrometrically at 340 nm. The bacterial-Gldh based l-glutamate assay was established, where the absorbance at 340 nm increased linearly with the increasing l-glutamate concentration within the range of 10 − 400 μM. Further, the proposed approach was successfully applied to measure l-glutamate in real samples.     

Studies on the genotoxic effect of chromium oxide (Cr VI): Interaction with deoxyribonucleic acid in solution

Chromium is a toxic and carcinogenic compound widely distributed in environment. In the present study we have investigated the interaction of chromium oxide with DNA employing UV/vis and fluorescence spectroscopy as well as Circular dichroism, thermal denaturation, retardation polyacrylamide gel electrophoresis and DNA-cellulose affinity techniques. The results showed that the binding of chromium oxide to DNA is concentration dependent; at low concentration shows a little effect but ant higher concentrations (>100 μg/ml) reduced the absorbance at 260 and 210 nm producing hypochromicity. Also λ_max of the metal at 210, 260 and 350 nm was reduced. DNA chromophores quenched with the chromium oxide and decreased fluorescence emission intensity. Upon binding of the metal to DNA the elliplicity at positive extreme was decreased (275 nm) and increased the ellipticity of the DNA at negative extreme 245 nm. Thermal denaturation profile of DNA shifted to higher degrees upon chromium oxide binding which accompanied by hypochromicity. Also, affinity of chromium oxide to double stranded DNA was higher than single stranded DNA. From the result it is concluded that chromium oxide interacts with DNA via two modes of interaction inducing structural changes and DNA compaction evidence providing chromium oxide genotoxicity.     

Antifungal potentiality of mycogenic silver nanoparticles capped with chitosan produced by endophytic Amesia atrobrunnea

This research reports the fabrication of silver nanoparticles (AgNPs) from endophytic fungus, Amesia atrobrunnea isolated from Ziziphus spina-christi (L.). Influencing factors for instance, thermal degree of incubation, media, pH, and silver nitrate (AgNO₃) molarity were optimized. Then, the AgNPs were encapsulated with chitosan (Ch-AgNPs) under microwave heating at 650 W for 90 s. Characterization of nanoparticles was performed via UV–visible (UV–vis) spectrophotometer, Fourier-transform infrared spectrophotometer (FTIR), zeta potential using dynamic-light scattering (DLS), and field-emission-scanning electron microscope (FE-SEM). Anti-fungal activity of Ch-AgNPs at (50, 25, 12.5, 6.25 mg/L) was tested against Fusarium oxysporum, Curvularia lunata, and Aspergillus niger using the mycelial growth inhibition method (MGI). Results indicated that Czapek-dox broth (CDB) with 1 mM AgNO₃, an acidic pH, and a temperature of 25–30 °C were the optimum for AgNPs synthesis. (UV–vis) showed the highest peak at 435 nm, whereas Ch-AgNPs showed one peak for AgNPs at 405 nm and another peak for chitosan at 230 nm. FTIR analysis confirmed that the capping agent chitosan was successfully incorporated and interacted with the AgNPs through amide functionalities. Z-potential was −19.7 mV for AgNPs and 38.9 mV for Ch-AgNPs, which confirmed the significant stability enhancement after capping. FES-SEM showed spherical AgNPs and a reduction in the nanoparticle size to 44.65 nm after capping with chitosan. The highest mycelial growth reduction using fabricated Ch-AgNPs was 93% for C. lunata followed by 77% for A. niger and 66% F. oxysporum at (50 mg/L). Biosynthesis of AgNPs using A. atrobrunnea cell-free extract was successful. Capping with chitosan exhibited antifungal activity against fungal pathogens.     

Aurein 2.3 functionality is supported by oblique orientated α-helical formation

In this study, an amphibian antimicrobial peptide, aurein 2.3, was predicted to use oblique orientated α-helix formation in its mechanism of membrane destabilisation. Molecular dynamic (MD) simulations and circular dichroism (CD) experimental data suggested that aurein 2.3 exists in solution as unstructured monomers and folds to form predominantly α-helical structures in the presence of a dimyristoylphosphatidylcholine membrane. MD showed that the peptide was highly surface active, which supported monolayer data where the peptide induced surface pressure changes > 34 mN m^? 1. In the presence of a lipid membrane MD simulations suggested that under hydrophobic mismatch the peptide is seen to insert via oblique orientation with a phenylalanine residue (PHE3) playing a key role in the membrane interaction. There is evidence of snorkelling leucine residues leading to further membrane disruption and supporting the high level of lysis observed using calcein release assays (76%). Simulations performed at higher peptide/lipid ratio show peptide cooperativity is key to increased efficiency leading to pore-formation.     

A novel MODIS algorithm to estimate chlorophyll a concentration in eutrophic turbid lakes

A novel approach was developed to estimate phytoplankton biomass in eutrophic turbid lakes, using MODIS bands designed for land and atmospheric studies. The Baseline Normalized Difference Bloom Index (BNDBI) uses the difference of remote-sensing reflectance (Rrs, sr⁻¹) at 555 nm (band 4) and 645 nm (band 1) after baseline correction using bands at 469 nm and 859 nm: (Rrs′(555) − Rrs′(645))/(Rrs′(555) + Rrs′(645)). BNDBI takes advantage of the Chl-a’s absorption minimum near 572 nm and absorption maximum near 667 nm. Using data from Lake Chaohu, the index showed a strong relationship with Chl-a concentrations in conditions that would normally saturate more sensitive ocean-color sensors. Extensive field measurements were used to calibrate and validate the algorithm with unbiased root-mean-square-error (URMSE) of 47.9% when compared to in situ Rrs data. A reduced sensitivity to atmospheric effects was accomplished by using a baseline correction approach, anchored at 469 nm and 859 nm to correct the radiances at 555 nm and 645 nm. Radiative transfer simulations showed that the algorithm can be applied directly to MODIS Rayleigh-corrected reflectance (Rrc) after adjusting algorithm coefficients (URMSE uncertainty of 56.4% for MODIS Rrc data) for Chl-a concentrations <1000 μg L⁻¹. Comparative analyses showed that the index was resistant to changes in turbidity and organic matter concentrations. Theoretical simulations, image comparisons and spectral analyses demonstrated that the index was robust in a range of complex atmospheric and surface conditions, with different aerosol types, optical thickness (τ_a555), solar/viewing geometry, sun glint and thin clouds. A comparison with other MODIS and MERIS Chl-a algorithms for turbid waters showed that BNDBI provided consistent results with the advantage of using MODIS wavebands that remain unsaturated in high turbidity conditions. The BNDBI opens new possibilities to explore bio-optical dynamics in turbid eutrophic lakes using data from a range of satellite sources.