A new approach for calculating microalgae culture growth based on an inhibitory effect of the surrounding biomass.

Ever since the potential of algae in biotechnology was recognized, models describing the growth of algae inside photobioreactors have been proposed. These models are the basis for the optimization of process conditions and reactor designs. Over the last few decades, models became more and more elaborate with the increase of computational capacity. Thus far, these models have been based on light attenuation due to the absorption and scattering effects of the biomass. This manuscript presents a new way of predicting the apparent growth inside photobioreactors using simple models for enzymatic kinetics to describe the reaction between photons and the photosynthetic unit. The proposed model utilizes an inhibition kinetic formula based on the surrounding biomass to describe the average growth rate of a culture, which is determined by the local light intensities inside the reactor. The result is a mixed-inhibition scheme with multiple inhibition sites. The parameters of the new kinetic equation are replaced by empirical regression functions to correlate their dependency on incident light intensity and reactor size. The calibrations of the parameters and the regression functions are based on the numerical solutions of the growth rate computed with a classical Type II model. As a final verification, we apply the new equation in predicting the growth behavior of three phototrophic organisms in reactors of three different sizes.

Evaluation of Chemical Interactions between Small Molecules in the Gas Phase Using Chemical Force Microscopy.

Chemical force microscopy analyzes the interactions between various chemical/biochemical moieties in situ. In this work we examined force-distance curves and lateral force to measure the interaction between modified AFM tips and differently functionalized molecular monolayers. Especially for the measurements in gas phase, we investigated the effect of humidity on the analysis of force-distance curves and the images in lateral force mode. Flat chemical patterns composed of different functional groups were made through micro-contact printing and lateral force mode provided more resolved analysis of the chemical patterns. From the images of 1-octadecanethiol/11-mercapto-1-undecanoic acid patterns, the amine group functionalized tip brought out higher contrast of the patterns than an intact silicon nitride tip owing to the additional chemical interaction between carboxyl and amine groups. For more complex chemical interactions, relative chemical affinities toward specific peptides were assessed on the pattern of 1-octadecanethiol/phenyl-terminated alkanethiol. The lateral image of chemical force microscopy reflected specific preference of a peptide to phenyl group as well as the hydrophobic interaction.

Delay in the recovery of normal sleep-wake cycle after disruption of the light-dark cycle in mice: a bipolar disorder-prone animal model?

OBJECTIVE: Disruption of the circadian rhythm is known as a provoking factor for manic episodes. Individual differences exist in the recovery rate from disruption in the general population. To develop a screening method to detect individuals vulnerable to bipolar disorder, the authors observed the relationship between the recovery of the normal sleep-wake cycle after switching the light-dark (LD) cycle and quinpirole-induced hyperactivity in mice. METHODS: Sixteen male mice (age of 5 weeks, weight 28-29 gm) were subjected to a circadian rhythm disruption protocol. Sleep-wake behaviors were checked every 5 min for a total duration of 15 days, i.e., 2 days of baseline observations, 3 days of LD cycle changes, and 10 days of recovery. During the dark cycle on the 16th experimental day, their general locomotor activities were measured in an open field for 120 minutes after an injection of quinpirole (0.5 mg/kg, s.c.). RESULTS: The individual differences in the recovery rate of the baseline sleep-wake cycle were noted after 3 days of switching the LD cycle. Fifty percent (n=8) of the mice returned to the baseline cycle within 6 days after normalizing the LD cycle (early recovery group). The locomotor activities of mice that failed to recover within 6 days (delayed recovery group) were significantly higher (mean rank=12.25) than those of the early recovery group (mean rank=4.75, u=62.0, p=0.001, Mann-Whitney U test). CONCLUSION: Given that the quinpirole-induced hyperactivity is an animal model of bipolar disorder, our results suggest individuals who have difficulties in recovery from circadian rhythm disruption may be vulnerable to bipolar disorder.

Facile diverted synthesis of pyrrolidinyl triazoles using organotrifluoroborate: discovery of potential mPTP blockers.

This article describes the rapid and diversified synthesis of pyrrolidinyl triazoles for the discovery of mitochondrial permeability transition pore (mPTP) blockers. The 1,3-dipolar cycloaddition of ethynyl trifluoroborate with azidopyrrolidine produced a key intermediate, triazolyl trifluoroborate 4, which subsequently underwent a Suzuki-Miyaura coupling reaction to afford a series of 1,4-disubstituted triazoles 2. Subsequent biological evaluation of these derivatives indicated 2ag and 2aj as the most potent mPTP blockers exhibiting excellent cytochrome P450 (CYP) stability when compared to the previously reported oxime analogue 1. The present work clearly demonstrates that a 1,2,3-triazole can be used as a stable oxime surrogate. Furthermore, it suggests that late-stage diversification through coupling reactions of organotrifluoroborates is suitable for the rapid discovery of biologically active molecules.

Mechanisms of prebiotic adenine synthesis from HCN by oligomerization in the gas phase.

We explored the potential energy surfaces for adenine synthesis by oligomerizations of HCN or HNC from CBS-QB3 calculations. The pathways have been obtained for the formation of the covalently bound HCN dimer, trimer, tetramer, and pentamer (adenine) by sequential additions of HCN or HNC. The activation energies of the individual oligomerization stages are a few hundred kilojoules per mole, which prevent efficient adenine synthesis in interstellar space or in the atmosphere of Titan. On the other hand, when the oligomerizations start from HCNH(+), the activation energies of sequential HCN or HNC additions are significantly reduced. Kinetic analyses results suggest that adenine synthesis by proton-catalyzed oligomerizations cannot occur efficiently in interstellar space or in the atmosphere of Titan, even though some oligomerization stages can occur under the latter condition.

Synthesis and evaluation of oxime derivatives as modulators for amyloid beta-induced mitochondrial dysfunction.

Starting from quinuclidinyl oxime 1 identified by preliminary screening, a series of azacycles-containing oxime derivatives was synthesized. Their mPTP blocking activities were evaluated by a JC-1 assay, measuring the change of mitochondrial membrane potential. The inhibitory activity of nine compounds against amyloid beta-induced mPTP opening was comparable or even superior to that of piracetam. Among them, 12d effectively maintained mitochondrial function and cell viabilities on the ATP assay, the MTT assay, and the ROS assay. In addition, it exhibited favorable in vitro stability and pharmacokinetic characteristics, which hold a promise for further development of AD therapeutics.

Glucosylation of the flavonoid, astragalin by Leuconostoc mesenteroides B-512FMCM dextransucrase acceptor reactions and characterization of the products.

Astragalin (kaempferol-3-O-ß-D-glucopyranoside, Ast) glucosides were synthesized by the acceptor reaction of a dextransucrase produced by Leuconostoc mesenteroides B-512FMCM with astragalin and sucrose. Each glucoside was purified and their structures were assigned as kaempferol-3-O-ß-D-glucopyranosyl-(1→3)-O-α-D-glucopyranoside (or kaempferol-3-O-ß-D-nigeroside, Ast-G1') and kaempferol-3-O-ß-D-glucopyranosyl-(1→6)-O-α-D-glucopyranoside (or kaempferol-3-O-ß-D-isomaltoside, Ast-G1) for one glucose transferred, and kaempferol-3-O-ß-D-isomaltooligosacharide (Ast-IMO or Ast-Gn; n=2-8). The astragalin glucosides exhibited 8.3-60.6% higher inhibitory effects on matrix metalloproteinase-1 expression, 18.8-20.3% increased antioxidant effects, and 3.8-18.8% increased inhibition activity of melanin synthesis compared to control (without the addition of compound), depending on the number of glucosyl residues linked to astragalin. These novel compounds could be used to further expand the industrial applications of astragalin glucosides, in particular in the cosmetics industry.

Inhibitory effects of epigallocatechin gallate and its glucoside on the human intestinal maltase inhibition.

Human intestinal maltase (HMA) is an α-glucosidase responsible for the hydrolysis of α-1,4-linkages from the non-reducing end of malto-oligosaccharides. HMA has become an important target in the treatment of type-2 diabetes. In this study, epigallocatechin gallate (EGCG) and EGCG glucoside (EGCG-G1) were identified as inhibitors of HMA by an in vitro assay with IC50 of 20 ± 1.0 and 31.5 ± 1.0 µM, respectively. A Lineweaver-Burk plot confirmed that EGCG and EGCG-G1 were competitive inhibitors of maltose substrate against HMA and inhibition kinetic constants (K i ) calculated from a Dixon plot were 5.93 ± 0.26 and 7.88 ± 0.57 µM, respectively. Both EGCG and EGCG-G1 bound to the active site of HMA with numerous hydrophobic and hydrogen bond interactions.

Enzymatic synthesis and characterization of hydroquinone galactoside using Kluyveromyces lactis lactase.

Hydroquinone galactoside (HQ-Gal) as a potential skin whitening agent was synthesized by the reaction of lactase (beta-galactosidase) from Kluyveromyces lactis, Aspergillus oryzae, Bacillus circulans, and Thermus sp. with lactose as a donor and HQ as an acceptor. Among these lactases, the acceptor reaction involving HQ and lactose with K. lactis lactase showed a higher conversion ratio to HQ-Gal (60.27%). HQ-Gal was purified using butanol partitioning and silica gel column chromatography. The structure of the purified HQ-Gal was determined by nuclear magnetic resonance, and the ionic product was observed at m/z 295 (C12H16O7Na)+ using matrix assisted laser desorption ionization time-of-flight mass spectrometry. HQ-Gal was identified as 4-hydroxyphenyl-beta-d-galactopyranoside. The optimum conditions for HQ-Gal synthesis by K. lactis determined using response surface methodology were 50 mM HQ, 60 mM lactose, and 20 U mL(-1) lactase. These conditions produced a yield of 2.01 g L(-1) HQ-Gal. The half maximal inhibitory concentration (IC50) of diphenylpicrylhydrazyl scavenging activity was 3.31 mM, indicating a similar antioxidant activity compared to beta-arbutin (IC50=3.95 mM). The Ki value of HQ-Gal (0.75 mM) against tyrosinase was smaller than that of beta-arbutin (Ki=1.97 mM), indicating its superiority as an inhibitor. HQ-Gal inhibited (23%) melanin synthesis without being significantly toxic to the cells, while beta-arbutin exhibited only 8% reduction of melanin synthesis in B16 melanoma cells compared with the control. These results indicate that HQ-Gal may be a suitable functional component in the cosmetics industry.