Fourier transform infrared spectrum of the secondary quinone electron acceptor Q(B) in photosystem II

Fourier transform infrared difference spectra upon single reduction of the secondary quinone electron acceptor Q(B) in photosystem II (PSII), without a contribution from the electron donor-side signals, were obtained for the first time using Mn-depleted PSII core complexes of the thermophilic cyanobacterium Thermosynechococcus elongatus. The Q(B)(-)/Q(B) difference spectrum exhibited a strong C...O stretching band of the semiquinone anion at 1480 cm(-)(1), the frequency higher by 2 cm(-)(1) than that of the corresponding band of Q(A)(-), in agreement with the previous S(2)Q(B)(-)/S(1)Q(B) spectrum of the PSII membranes of spinach [Zhang, H., Fischer, G., and Wydrzynski, T. (1998) Biochemistry 37, 5511-5517]. Also, several peaks originating from the Fermi resonance of coupled His modes with its strongly H-bonded NH vibration were observed in the 2900-2600 cm(-)(1) region, where the peak frequencies were higher by 7-24 cm(-)(1) compared with those of the Q(A)(-)/Q(A) spectrum. These frequency differences suggest that H-bond interactions of the CO groups, especially with a His side chain, are different between Q(B)(-) and Q(A)(-). Furthermore, a prominent positive peak was observed at 1745 cm(-)(1) in the C=O stretching region of COOH or ester groups in the Q(B)(-)/Q(B) spectrum. The peak frequency was unaffected by D(2)O substitution, indicating that this peak does not arise from a COOH group but probably from the 10a-ester C=O group of the pheophytin molecule adjacent to Q(B). The absence of protonation of carboxylic amino acids upon Q(B)(-) formation in contrast to the previous observation in the purple bacterium Rhodobacter sphaeroides suggests that the protonation mechanism of Q(B) in PSII is different from that of bacterial reaction centers.     

Saturated fatty acid and TLR signaling link β cell dysfunction and islet inflammation

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Highlights? Palmitate induces β cell dysfunction by activating inflammatory processes in islets ? β cells sense palmitate via the TLR4 pathway and recruit M1 macrophages to islets ? M1 macrophages play a pivotal role in palmitate-induced β cell dysfunction ? M1 macrophages and inflammation also play a role in β cell dysfunction in T2D models     

Whole cell segmentation in solid tissue sections.

BACKGROUND: Understanding the cellular and molecular basis of tissue development and function requires analysis of individual cells while in their tissue context. METHODS: We developed software to find the optimum border around each cell (segmentation) from two-dimensional microscopic images of intact tissue. Samples were labeled with a fluorescent cell surface marker so that cell borders were brighter than elsewhere. The optimum border around each cell was defined as the border with an average intensity per unit length greater that any other possible border around that cell, and was calculated using the gray-weighted distance transform. Algorithm initiation requiring the user to mark two points per cell, one approximately in the center and the other on the border, ensured virtually 100% correct segmentation. Thereafter segmentation was automatic. RESULTS: The method was highly robust, because intermittent labeling of the cell borders, diffuse borders, and spurious signals away from the border do not significantly affect the optimum path. Computer-generated cells with increasing levels of added noise showed that the approach was accurate provided the cell could be detected visually. CONCLUSIONS: We have developed a highly robust algorithm for segmenting images of surface-labeled cells, enabling accurate and quantitative analysis of individual cells in tissue.     

Selective recovery of precious metals by persimmon waste chemically modified with dimethylamine

Persimmon waste was chemically modified with dimethylamine (DMA) to obtain a tertiary-amine-type gel, named DMA persimmon waste gel (DMA-PW). It was found to be effective for the adsorption of Au(III), Pd(II), and Pt(IV) in hydrochloric acid medium. In contrast, base metals such as Cu(II), Zn(II), Fe(III), and Ni(II) were not practically adsorbed. The formation of ion pairs of the metal chloro complex anions with the protonated adsorption gels was proposed as the main adsorption process. The gel exhibited selectivity only for precious metals with a remarkably high capacity for Au(III), i.e., 5.63 mol/kg dry gel and comparable capacities, i.e., 0.42 and 0.28 mol/kg for Pd(II) and Pt(IV), respectively. According to the kinetic and electrochemical studies, the adsorption rate of Au(III) was greatly enhanced by the chemical modification. Also, its excellent adsorption characteristics for the precious metals were confirmed by adsorption and elution tests using a column packed with the DMA-PW gel.     

Autotaxin/Lysophospholipase D-mediated Lysophosphatidic Acid Signaling Is Required to Form Distinctive Large Lysosomes in the Visceral Endoderm Cells of the Mouse Yolk Sac

Autotaxin, a lysophospholipase D encoded by the Enpp2 gene, is an exoenzyme that produces lysophosphatidic acid in the extracellular space. Lysophosphatidic acid acts on specific G protein-coupled receptors, thereby regulating cell growth, migration, and survival. Previous studies have revealed that Enpp2^−/− mouse embryos die at about embryonic day (E) 9.5 because of angiogenic defects in the yolk sac. However, what cellular defects occur in Enpp2^−/− embryos and what intracellular signaling pathways are involved in the phenotype manifestation remain unknown. Here, we show that Enpp2 is required to form distinctive large lysosomes in the yolk sac visceral endoderm cells. From E7.5 to E9.5, Enpp2 mRNA is abundantly expressed in the visceral endoderm cells. In Enpp2^−/− mouse embryos, lysosomes in the visceral endoderm cells are fragmented. By using a whole embryo culture system combined with specific pharmacological inhibitors for intracellular signaling molecules, we show that lysophosphatidic acid receptors and the Rho-Rho-associated coiled-coil containing protein kinase (ROCK)-LIM kinase pathway are required to form large lysosomes. In addition, electroporation of dominant negative forms of Rho, ROCK, or LIM kinase also leads to the size reduction of lysosomes in wild-type visceral endoderm cells. In Enpp2^−/− visceral endoderm cells, the steady-state levels of cofilin phosphorylation and actin polymerization are reduced. In addition, perturbations of actin turnover dynamics by actin inhibitors cytochalasin B and jasplakinolide result in the defect in lysosome formation. These results suggest that constitutive activation of the Rho-ROCK-LIM kinase pathway by extracellular production of lysophosphatidic acid by the action of autotaxin is required to maintain the large size of lysosomes in visceral endoderm cells.     

Canopy ergodicity: can a single leaf represent an entire plant canopy?

While leaves typically emerge near shoot apices around the outer surface of a plant canopy, their relative position “moves” deeper into the canopy as additional leaves emerge. The photosynthetic capacity (A _max) of a given leaf can be expected to decline over time as its relative position (P _r) in the canopy becomes progressively deeper; this can be observed as a spatial gradient with the A _max of leaves declining distally from the shoot apex. As a consequence, we propose that the photosynthetic capacity averaged over a single leaf’s lifespan is equivalent to the average photosynthetic capacity of the entire plant canopy at a given time; in other words, there is an ergodic time to space averaging in the organization and development of plant canopies. We tested this “canopy ergodic hypothesis” in two woody (Alnus sieboldiana and Mallotus japonica) and two herbaceous (Polygonum sachalinensis and Helianthus tuberosus) species by following the photosynthetic capacity in 100 individual leaves from the time of their emergence until their death. We compared the average photosynthetic capacity of individual leaves through time (time-average) to the average photosynthetic capacity of all the leaves along a shoot at the time of emergence of the focal leaf (space-average). We found that A _max and P _r were positively correlated and that the time-averages of three plant species (Alnus, Mallotus, and Helianthus) were not significantly different from the corresponding space-averages, although the averages differed among individual plants. Polygonum, however, did show significant differences between time and space averages. Ergodicity appears to apply to the leaf–canopy relationship, at least approximately—the average photosynthetic capacity of a single leaf through time (time-average) can represent the average photosynthetic capacity of the entire canopy.     

BBX32, an Arabidopsis B-Box protein, functions in light signaling by suppressing HY5-regulated gene expression and interacting with STH2/BBX21

A B-box zinc finger protein, B-BOX32 (BBX32), was identified as playing a role in determining hypocotyl length during a large-scale functional genomics study in Arabidopsis (Arabidopsis thaliana). Further analysis revealed that seedlings overexpressing BBX32 display elongated hypocotyls in red, far-red, and blue light, along with reduced cotyledon expansion in red light. Through comparative analysis of mutant and overexpression line phenotypes, including global expression profiling and growth curve studies, we demonstrate that BBX32 acts antagonistically to ELONGATED HYPOCOTYL5 (HY5). We further show that BBX32 interacts with SALT TOLERANCE HOMOLOG2/BBX21, another B-box protein previously shown to interact with HY5. Based on these data, we propose that BBX32 functions downstream of multiple photoreceptors as a modulator of light responses. As such, BBX32 potentially has a native role in mediating gene repression to maintain dark adaptation.     

Biochemical synthesis of novel,self-assembling glycolipids from ricinoleic acid by a recombinant α-glucosidase from <Emphasis Type="Italic">Geobacillus</Emphasis> sp.

Purpose of work  

To explore a novel glycolipid, we performed biochemical reactions using a recombinant α-glucosidase from Geobacillus sp. which shows excellent transglycosylation reaction to hydroxyl groups in a variety of compounds.