Selective protection of glycinebetaine on extrinsic polypeptides of PS II particles

1997 ◽  
Vol 42 (20) ◽  
pp. 1744-1748 ◽  
Author(s):  
Caixia Hou ◽  
Chunhe Xu ◽  
Zhangcheng Tang ◽  
Yunkang Shen
Keyword(s):  
Ps Ii ◽  
Selective Protection ◽  
Extrinsic Polypeptides

Surface Charge Density Changes in Isolated Photosystem II Membranes Induced by Depletion of the Extrinsic Polypeptides of the Oxygen Evolving System

1990 ◽  
Vol 45 (6) ◽  
pp. 627-632 ◽  
Author(s):  
Alexander G. Ivanov ◽  
Mira C. Busheva ◽  
Maya Y. Velitchkova
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Surface Charge Density ◽  
Oxygen Evolving Complex ◽  
Partial Recovery ◽  
Ps Ii ◽  
Extrinsic Polypeptides ◽  
Evolving System ◽  
Oxygen Evolving System ◽  
Oxygen Evolving

Abstract Treatment of PS II particles with either 1 M NaCl or alkaline Tris (1 M , pH 8.4) caused a considerable decrease in the average net negative surface charge density, concomitant with depletion of the extrinsic 17, 24 and 33 kDa proteins of the oxygen evolving complex from the membranes. The partial recovery of the values for surface charge in both NaCl- and Tris-treated membranes was registered after reconstitution experiments with the three proteins. These results are compared with the data for the charge densities of the thylakoid membranes, to examine the role of the three extrinsic proteins in the formation of heterogeneous arrangement of surface charge across the appressed (granal) thylakoids.

Effect of TCA-depletion of extrinsic polypeptides on electron transport on oxidizing side of PS II

1997 ◽  
Vol 42 (3) ◽  
pp. 227-231
Author(s):  
Rong Li ◽  
Yungang Shen ◽  
Chunhe Xu ◽  
Wei Lu ◽  
Tiecheng Tu ◽  
...  
Keyword(s):  
Electron Transport ◽  
Ps Ii ◽  
Extrinsic Polypeptides

The effects of calcium depletion on the O2-evolving complex in spinach PS II: The S∗1, S∗2 and S∗3 states and the role of the 17 kDa and 23 kDa extrinsic polypeptides

1994 ◽  
Vol 1186 (3) ◽  
pp. 186-200 ◽  
Author(s):  
Dugald J. MacLachlan ◽  
Jonathan H.A. Nugent ◽  
Peter J. Bratt ◽  
Michael C.W. Evans
Keyword(s):  
Calcium Depletion ◽  
Ps Ii ◽  
Extrinsic Polypeptides

Europium- and Dysprosium-Ions as Probes for the Study of Calcium Binding Sites in Photosystem II

1995 ◽  
Vol 50 (3-4) ◽  
pp. 220-230 ◽  
Author(s):  
K. Burda ◽  
K. Strzałka ◽  
G. H. Schmid
Keyword(s):  
Photosystem Ii ◽  
Binding Sites ◽  
Calcium Binding ◽  
Lanthanide Ions ◽  
Ps Ii ◽  
Trivalent Lanthanide ◽  
Lanthanide Cations ◽  
Extrinsic Polypeptides ◽  
Calcium Binding Sites ◽  
Mn Cluster

Trivalent lanthanide cations are suitable probes for Ca2+-binding sites in photosystem II (PS II). PS II membranes prepared from Nicoticinci tabacum, intact and depleted of the extrinsic polypeptides were exposed to lanthanide ions (Dy3+ and Eu3+). Small concentrations of dysprosium and europium ions enhance oxygen evolution under short saturating flashes. Higher concentrations of the rare earth cations cause the release of the three extrinsic peptides (17, 23 and 33 kDa) and reduce O2 yield. The reactivation of the PS II membranes, thus depleted of the 33 kDa subunit, by Ca2+ ions is not possible. Comparing Eu3+ with Dy3+ in this effect shows that Eu3+ is more effective than Dy3+, because a lower Eu3+-concentration in comparison to that of Dy3+ inactivates O2-evolution. The differences between europium and dysprosium can be explained by their different ionic radius. Our results suggest the existence of two Ca-binding regions: one with a low affinity for calcium would be located on the contact surface of the 23 and 33 kDa proteins and the second one with a high affinity, should be located close to the Mn-cluster and to tyrosine-161 (Z ). The more tightly-bound calcium would be responsible for the activity of the PS II system.

Nuances in Alzheimer’s Genetic Risk Reveal Differential Predictions of Non-demented Memory Aging Trajectories: Selective Patterns by APOE Genotype and Sex

2019 ◽  
Vol 16 (4) ◽  
pp. 302-315 ◽  
Author(s):  
G. Peggy McFall ◽  
Lars Bäckman ◽  
Roger A. Dixon
Keyword(s):  
Genetic Risk ◽  
Growth Models ◽  
Memory Performance ◽  
Apoe Genotype ◽  
Cognitively Impaired ◽  
Latent Growth ◽  
Latent Growth Models ◽  
Selective Protection ◽  
Underlying Mechanisms ◽  
Apoe Genotypes

Background: Apolipoprotein E (APOE) is a prominent genetic risk factor for Alzheimer’s disease (AD) and a frequent target for associations with non-demented and cognitively impaired aging. APOE offers a unique opportunity to evaluate two dichotomous comparisons and selected gradations of APOE risk. Some evidence suggests that APOE effects may differ by sex and emerge especially in interaction with other AD-related biomarkers (e.g., vascular health). Methods: Longitudinal trajectories of non-demented adults (n = 632, 67% female, Mage = 68.9) populated a 40-year band of aging. Focusing on memory performance and individualized memory trajectories, a sequence of latent growth models was tested for predictions of (moderation between) APOE and pulse pressure (PP) as stratified by sex. The analyses (1) established robust benchmark PP effects on memory trajectories, (2) compared predictions of alternative dichotomous groupings (ε4- vs ε4+, ε2- vs ε2+), and (3) examined precision-based predictions by disaggregated APOE genotypes. Results: Healthier (lower) PP was associated with better memory performance and less decline. Therefore, all subsequent analyses were conducted in the interactive context of PP effects and sex stratification. The ε4-based dichotomization produced no differential genetic predictions. The ε2-based analyses showed sex differences, including selective protection for ε2-positive females. Exploratory follow-up disaggregated APOE genotype analyses suggested selective ε2 protection effects for both homozygotic and heterozygotic females. Conclusion: Precision analyses of AD genetic risk will advance the understanding of underlying mechanisms and improve personalized implementation of interventions.

Hafnium(IV) Chloride Catalyzes Highly Efficient Acetalization of Carbonyl Compounds

2019 ◽  
Vol 16 (6) ◽  
pp. 913-920 ◽  
Author(s):  
Israel Bonilla-Landa ◽  
Emizael López-Hernández ◽  
Felipe Barrera-Méndez ◽  
Nadia C. Salas ◽  
José L. Olivares-Romero
Keyword(s):  
Microwave Heating ◽  
Reaction Times ◽  
Protecting Groups ◽  
Catalyst Loading ◽  
Selective Protection ◽  
Highly Efficient ◽  
Aldehydes And Ketones ◽  
High Yields ◽  
Novel Catalyst ◽  
Acid Labile

Background: Hafnium(IV) tetrachloride efficiently catalyzes the protection of a variety of aldehydes and ketones, including benzophenone, acetophenone, and cyclohexanone, to the corresponding dimethyl acetals and 1,3-dioxolanes, under microwave heating. Substrates possessing acid-labile protecting groups (TBDPS and Boc) chemoselectively generated the corresponding acetal/ketal in excellent yields. Aim and Objective: In this study. the selective protection of aldehydes and ketones using a Hafnium(IV) chloride, which is a novel catalyst, under microwave heating was observed. Hence, it is imperative to find suitable conditions to promote the protection reaction in high yields and short reaction times. This study was undertaken not only to find a novel catalyst but also to perform the reaction with substrates bearing acid-labile protecting groups, and study the more challenging ketones as benzophenone. Materials and Methods: Using a microwave synthesis reactor Monowave 400 of Anton Paar, the protection reaction was performed on a raging temperature of 100°C ±1, a pressure of 2.9 bar, and an electric power of 50 W. More than 40 substrates have been screened and protected, not only the aldehydes were protected in high yields but also the more challenging ketones such as benzophenone were protected. All the products were purified by simple flash column chromatography, using silica gel and hexanes/ethyl acetate (90:10) as eluents. Finally, the protected substrates were characterized by NMR 1H, 13C and APCI-HRMS-QTOF. Results: Preliminary screening allowed us to find that 5 mol % of the catalyst is enough to furnish the protected aldehyde or ketone in up to 99% yield. Also it was found that substrates with a variety of substitutions on the aromatic ring (aldehyde or ketone), that include electron-withdrawing and electrondonating group, can be protected using this methodology in high yields. The more challenging cyclic ketones were also protected in up to 86% yield. It was found that trimethyl orthoformate is a very good additive to obtain the protected acetophenone. Finally, the protection of aldehydes with sensitive functional groups was performed. Indeed, it was found that substrates bearing acid labile groups such as Boc and TBDPS, chemoselectively generated the corresponding acetal/ketal compound while keeping the protective groups intact in up to 73% yield. Conclusion: Hafnium(IV) chloride as a catalyst provides a simple, highly efficient, and general chemoselective methodology for the protection of a variety of structurally diverse aldehydes and ketones. The major advantages offered by this method are: high yields, low catalyst loading, air-stability, and non-toxicity.

scholarly journals Selective protection of human cardiomyocytes from anthracycline cardiotoxicity by small molecule inhibitors of MAP4K4

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Pelin A. Golforoush ◽  
Priyanka Narasimhan ◽  
Patricia P. Chaves-Guerrero ◽  
Elsa Lawrence ◽  
Gary Newton ◽  
...  
Keyword(s):  
Small Molecule ◽  
Small Molecule Inhibitors ◽  
Anthracycline Cardiotoxicity ◽  
Human Cardiomyocytes ◽  
Selective Protection

Isolierung von PS II-Partikeln mit in vivo Eigenschaften aus Euglena gracilis, Stamm Z / Isolation of PS II-Particels with in vivo Characteristics from Euglena gracilis, Stamm Z

1982 ◽  
Vol 37 (3-4) ◽  
pp. 256-259 ◽  
Author(s):  
F. Schuler ◽  
P. Brandt ◽  
W. Wießner
Keyword(s):  
Euglena Gracilis ◽  
Fluorescence Emission ◽  
Improved Method ◽  
Ps Ii ◽  
Ps I ◽  
Emission And Absorption Spectra ◽  
Chlorophyll Protein ◽  
Ps Ii Activity ◽  
Photosystem Ii Particles

Abstract An improved method for isolation of (photosystem II)-particles from Euglena gracilis, strain Z was established. PS II-particles isolated by ultrasonic treatment and following differential centrifugation show fluorescence emission and absorption spectra identical with in vivo properties of Euglena gracilis. These PS II-particles have only PS II-activity and contain CP a, the typical chlorophyll-protein-complex of PS II. No contamination of PS I-components are detectable.

Photosystem II Inhibition by Pyran-enamine Derivatives

1993 ◽  
Vol 48 (3-4) ◽  
pp. 163-167
Author(s):  
Koichi Yoneyama ◽  
Yoshihiro Nakajima ◽  
Masaru Ogasawara ◽  
Hitoshi Kuramochi ◽  
Makoto Konnai ◽  
...  
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Thylakoid Membranes ◽  
Major Determinant ◽  
Ps Ii ◽  
Structure Activity Relationships ◽  
Structure Activity

Abstract Through the studies on structure-activity relationships of 5-acyl-3-(1-aminoalkylidene)-4-hydroxy-2 H-pyran-2,6(3 H)-dione derivatives in photosystem II (PS II) inhibition, overall lipophilicity of the molecule was found to be a major determinant for the activity. In the substituted N -benzyl derivatives, not only the lipophilicity but also the electronic and steric characters of the substituents greatly affected the activity. Their mode of PS II inhibition seemed to be similar to that of DCMU , whereas pyran-enamine derivatives needed to be highly lipophilic to block the electron transport in thylakoid membranes, which in turn diminished the permeability through biomembranes.

In situ selective protection of aldehydes via aldemides. Simple conversions of ketoaldehydes to methylene aldehydes and to methylhydroxy aldehydes.

Tetrahedron ◽  
1984 ◽  
Vol 40 (2) ◽  
pp. 267
Author(s):  
G. Pagani Zecchini ◽  
M. Paglialunga Paradisi ◽  
I. Torrini
Keyword(s):  
Selective Protection
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