Structural effects on epimerization of bacteriochlorophyll a and chlorophyll a revealed using 3-acetyl chlorophyll a

2020 ◽  
Vol 24 (04) ◽  
pp. 499-504 ◽  
Author(s):  
Yoshitaka Saga ◽  
Shiori Nakagawa
Keyword(s):  
Physicochemical Properties ◽  
Chlorophyll A ◽  
Photosynthetic Reaction Center ◽  
Molecular Structures ◽  
Structural Factors ◽  
Structural Effects ◽  
Photosynthetic Organisms ◽  
Acetyl Group ◽  
Kinetics Of

Chlorophyll (Chl) and bacteriochlorophyll (BChl) pigments, which are crucial cyclic tetrapyrroles in photosynthesis, generally have a chiral center in their exo-cyclic five-membered E-ring. Although [Formula: see text]-epimers (primed-type) of (B)Chl pigments are rarely present in photosynthetic organisms, they play key roles in photosynthetic reaction center complexes. The epimerization mechanism of (B)Chl pigments in vivo has not been unraveled. The structural effects on the physicochemical properties of (B)Chl epimerization reactions provide useful information to tackle this question. We analyzed epimerization of three pigments, BChl [Formula: see text], Chl [Formula: see text], and 3-acetyl Chl [Formula: see text], to elucidate the structural factors that are responsible for epimerization reactions. We compared the epimerization kinetics of the three pigments and concluded that the bacteriochlorin skeleton (7,8,17,18-tetrahydroporphyrin) significantly retarded the epimerization kinetics. Thus, BChl [Formula: see text] exhibited slower epimerization kinetics than Chl [Formula: see text] in spite of the presence of the electron-withdrawing 3-acetyl group that accelerates epimerization. In contrast to the large structural effects of (B)Chl molecules on epimerization kinetics, the thermodynamic properties at equilibrium in the epimerization of the three pigments were barely influenced by their molecular structures. This study also demonstrates that a semi-synthetic pigment, 3-acetyl Chl [Formula: see text], is appropriate for comparative analyses of the structural effects of BChl [Formula: see text] and Chl [Formula: see text] on their physicochemical properties.

Structural effects in chemistry and biology

2000 ◽  
Vol 04 (04) ◽  
pp. 382-385 ◽  
Author(s):  
JACK FAJER
Keyword(s):  
Excited State ◽  
Physicochemical Properties ◽  
Crystal Structures ◽  
Protein Complexes ◽  
Structural Effects ◽  
Conformational Variations ◽  
Prosthetic Groups ◽  
Skeletal Deformations

Conformationally designed, non-planar porphyrins afford new classes of structurally distinct chromophores with significantly altered optical, redox, magnetic, radical and excited state properties. The synthetic, non-planar porphyrins model and illustrate the consequences of the skeletal deformations and plasticity increasingly observed in crystal structures of protein complexes comprising porphyrinic chromophores and prosthetic groups. Conformational variations thus offer attractively simple mechanisms for modulating the physicochemical properties of porphyrins in vivo and in vitro.

Three types of alpha-melanocyte-stimulating hormone: bioactivities and half-lives

1983 ◽  
Vol 245 (1) ◽  
pp. E47-E54 ◽  
Author(s):  
D. Rudman ◽  
B. M. Hollins ◽  
M. H. Kutner ◽  
S. D. Moffitt ◽  
M. J. Lynn
Keyword(s):  
Tissue Slices ◽  
Melanocyte Stimulating Hormone ◽  
Lipolytic Action ◽  
Acetyl Group ◽  
Isolated Adipocytes ◽  
Hydroxy Groups ◽  
Kinetics Of ◽  
Stimulating Hormone

Three types of alpha-melanocyte-stimulating hormone (alpha MSH) that differ in the acetyl status of the N-terminal serine have been found in the neurointermediate lobe of the pituitary gland and in the brain: desacetyl alpha MSH, which lacks an acetyl group; monoacetyl alpha MSH, in which the amino group of the serine is acetylated; and diacetyl alpha MSH, in which both amino and hydroxy groups of the serine are acetylated. We compared the lipolytic and melanotropic actions of these three peptides, and their rates of disappearance from plasma, both in vitro and in vivo. The following differences were found. a) For in vitro lipolytic actions on rabbit adipose tissue slices, the potencies differed according to the order diacetyl = monoacetyl greater than desacetyl. On rabbit isolated adipocytes, however, the three peptides were equipotent. b) For in vivo lipolytic action in the rabbit, not only potency but also kinetics differed. Diacetyl alpha MSH had the slowest onset, longest duration, and greatest potency. The desacetyl variant had the quickest onset, shortest duration, and least potency. c) The half-life for elimination from rabbit plasma both in vitro and in vivo was shortest for the desacetyl form and longest for the diacetyl peptide. d) For in vitro melanotropic effect on frog skin, kinetics of action were the same for all three peptides, but potency differed according to the order diacetyl = monoacetyl greater than desacetyl. Thus acetylation of alpha MSH alters lipolytic and melanotropic potencies in vitro and lipolytic potency and kinetics in vivo. These differences result in part from the fact that acetylation slows the degradation of the tridecapeptide both inside and outside the circulation.

DEVELOPMENT OF A PHOTOSENSITIZER DELIVERY SYSTEM FOR THERAPY AND DIAGNOSTICS IN ONCOLOGY

2020 ◽  
pp. 124-125
Author(s):  
A.Semkina Semkina ◽  
M.Abakumov Abakumov ◽  
P.Ostroverkhov Ostroverkhov ◽  
M. Grin
Keyword(s):  
Photodynamic Therapy ◽  
Physicochemical Properties ◽  
Tumor Cells ◽  
Therapeutic Effect ◽  
Delivery System ◽  
Biological Studies ◽  
Kinetics Of ◽  
Ct26 Tumor

In this work, the MNP-HSA-PEG-PS@4 complex was obtained and its physicochemical properties were studied. Biological studies have also been conducted. Namely, the ability of the drug to accumulate in CT26 tumor cells in vitro and the kinetics of drug accumulation in the tumor in vivo were studied. Then, the effectiveness of photodynamic therapy was studied under different conditions. The maximum therapeutic effect was achieved with irradiation at 1 hour after injection of the drug.

scholarly journals Electron flow through NDH-1 complexes is the major driver of cyclic electron flow-dependent proton pumping in cyanobacteria

2020 ◽  
Author(s):  
Neil T. Miller ◽  
Michael D. Vaughn ◽  
Robert L. Burnap
Keyword(s):  
Electron Flow ◽  
Proton Pumping ◽  
Cyclic Electron Flow ◽  
Pumping Rate ◽  
Photosynthetic Organisms ◽  
Photosynthetic Electron Flow ◽  
Flow Through ◽  
Pumping Rates ◽  
Kinetics Of

AbstractCyclic electron flow (CEF) around Photosystem I is vital to balancing the photosynthetic energy budget of cyanobacteria and other photosynthetic organisms. The coupling of CEF to proton pumping has long been hypothesized to occur, providing proton motive force (PMF) for the synthesis of ATP with no net cost to [NADPH]. This is thought to occur largely through the activity of NDH-1 complexes, of which cyanobacteria have four with different activities. While a much work has been done to understand the steady-state PMF in both the light and dark, and fluorescent probes have been developed to observe these fluxes in vivo, little has been done to understand the kinetics of these fluxes, particularly with regard to NDH-1 complexes. To monitor the kinetics of proton pumping in Synechocystis sp. PCC 6803, the pH sensitive dye Acridine Orange was used alongside a suite of inhibitors in order to observe light-dependent proton pumping. The assay was demonstrated to measure photosynthetically driven proton pumping and used to measure the rates of proton pumping unimpeded by dark ΔpH. Here, the cyanobacterial NDH-1 complexes are shown to pump a sizable portion of proton flux when CEF-driven and LEF-driven proton pumping rates are observed and compared in mutants lacking some or all NDH-1 complexes. It is also demonstrated that PSII and LEF are responsible for the bulk of light induced proton pumping, though CEF and NDH-1 are capable of generating ∼40% of the proton pumping rate when LEF is inactivated.Highlights statementNDH-1 is essential for proton pumping during cyclic photosynthetic electron flow in cyanobacteria

Utilization of induction and quenching kinetics of chlorophyll a fluorescence for in vivo salinity screening studies in wheat (Triticum aestivum vars. Kharchia-65 and Fielder)

1993 ◽  
Vol 71 (1) ◽  
pp. 87-92 ◽  
Author(s):  
Sankaran KrishnaRaj ◽  
Bruce T. Mawson ◽  
Edward C. Yeung ◽  
Trevor A. Thorpe
Keyword(s):  
Triticum Aestivum ◽  
Salt Stress ◽  
Chlorophyll A ◽  
Chlorophyll A Fluorescence ◽  
Triticum Aestivum L ◽  
Fluorescence Signal ◽  
Salt Tolerant ◽  
In Vivo Screening ◽  
Kinetics Of

The potential of utilizing induction and quenching kinetics of chlorophyll a fluorescence as consistent and reliable markers for in vivo salt (sodium sulphate) tolerance screening studies was investigated by comparing two wheat (Triticum aestivum L.) varieties with varying responses to salinity, viz. Kharchia-65 (salt-tolerant) and Fielder (salt-susceptible). Three-week-old seedlings were treated with a range of salt concentrations (0 to 2%) over a 1- to 2-week period. Both the maximum rates of fluorescence induction and quenching measured from leaf sections decreased significantly in Fielder compared with Kharchia-65 as the salt concentration increased. Alterations in other fluorescence parameters, such as the maximum yield of fluorescence signal in the absence and presence of 3(3,4-dichlorophenyl)-1,1-dimethylurea by the variety Fielder indicated a minimal reduction in the size of the primary electron acceptor pool associated with photosystem II following salt stress. In contrast, these parameters were altered to a lesser extent by salt treatments in Kharchia-65. The effect of salinity stress on leaf morphology of both varieties indicated no major anatomical alterations apart from a negligible increase in leaf thickness. Total chlorophyll content of Kharchia-65 increased significantly as a result of salt stress, owing to an increase in both chlorophyll a and chlorophyll b, whereas Fielder showed no significant variations. The results indicate that total fluorescence quenching and maximum rates of both induction and quenching appear to be reliable indicators for in vivo screening of salt-tolerant wheat genotypes. Key words: Triticum aestivum L., wheat, chlorophyll a fluorescence, salt stress, in vivo screening.

Effect of pH and inhibitors on beta-amyloid fibril assembly

1996 ◽  
Vol 54 ◽  
pp. 752-753
Author(s):  
Beverly E. Maleeff ◽  
Timothy K. Hart ◽  
Stephen J. Wood ◽  
Ronald Wetzel
Keyword(s):  
Amyloid Fibril ◽  
Peptide Fragment ◽  
Hydrophobic Peptides ◽  
Amyloid Fibril Formation ◽  
Effects Of Ph ◽  
Severity Of The Disease ◽  
Kinetics Of ◽  
The Brain

Alzheimer's disease is characterized post-mortem in part by abnormal extracellular neuritic plaques found in brain tissue. There appears to be a correlation between the severity of Alzheimer's dementia in vivo and the number of plaques found in particular areas of the brain. These plaques are known to be the deposition sites of fibrils of the protein β-amyloid. It is thought that if the assembly of these plaques could be inhibited, the severity of the disease would be decreased. The peptide fragment Aβ, a precursor of the p-amyloid protein, has a 40 amino acid sequence, and has been shown to be toxic to neuronal cells in culture after an aging process of several days. This toxicity corresponds to the kinetics of in vitro amyloid fibril formation. In this study, we report the biochemical and ultrastructural effects of pH and the inhibitory agent hexadecyl-N-methylpiperidinium (HMP) bromide, one of a class of ionic micellar detergents known to be capable of solubilizing hydrophobic peptides, on the in vitro assembly of the peptide fragment Aβ.

Kinetics of Various 99mTc-Sn-Pyrophosphate Compounds in the Rat

1977 ◽  
Vol 16 (04) ◽  
pp. 157-162 ◽  
Author(s):  
C. Schümichen ◽  
B. Mackenbrock ◽  
G. Hoffmann
Keyword(s):  
Normal Saline ◽  
Half Life ◽  
Compound A ◽  
Short Half Life ◽  
Low Concentrations ◽  
The Stability ◽  
Kinetics Of ◽  
In Vitro Stability

SummaryThe bone-seeking 99mTc-Sn-pyrophosphate compound (compound A) was diluted both in vitro and in vivo and proved to be unstable both in vitro and in vivo. However, stability was much better in vivo than in vitro and thus the in vitro stability of compound A after dilution in various mediums could be followed up by a consecutive evaluation of the in vivo distribution in the rat. After dilution in neutral normal saline compound A is metastable and after a short half-life it is transformed into the other 99mTc-Sn-pyrophosphate compound A is metastable and after a short half-life in bone but in the kidneys. After dilution in normal saline of low pH and in buffering solutions the stability of compound A is increased. In human plasma compound A is relatively stable but not in plasma water. When compound B is formed in a buffering solution, uptake in the kidneys and excretion in urine is lowered and blood concentration increased.It is assumed that the association of protons to compound A will increase its stability at low concentrations while that to compound B will lead to a strong protein bond in plasma. It is concluded that compound A will not be stable in vivo because of a lack of stability in the extravascular space, and that the protein bond in plasma will be a measure of its in vivo stability.

Hepatobiliary Kinetics of 113mIn-Phenolphthalexon

1981 ◽  
Vol 20 (02) ◽  
pp. 90-93
Author(s):  
P.B. Parab ◽  
U.R. Raikar ◽  
R.D. Ganatra ◽  
M. C. Patel
Keyword(s):  
Biliary Excretion ◽  
Iminodiacetic Acid ◽  
Organ Distribution ◽  
Liver Uptake ◽  
On Line ◽  
Rapid Clearance ◽  
Chemical Purity ◽  
Kinetics Of ◽  
High Liver

Phenolphthalexon, a compound with iminodiacetic acid as a functional group, has been labelled with 113mIn to high chemical purity and its usefulness in studies of biliary excretion patency has been studied. Organ distribution of 113mIn-phenolphthalexon in mice was characterized by high liver uptake (50.8% of the administered dose after 5 min) and rapid clearance through the gall bladder. An animal model for studying obstruction of biliary excretion has been developed. Data on the kinetics of the radiopharmaceutical were obtained by collecting in-vivo data through an on-line computer.

Continuous Quantitative Monitoring of Mural, Platelet-Dependent, Thrombus Kinetics in the Crushed Rat Femoral Vein

1991 ◽  
Vol 65 (04) ◽  
pp. 425-431 ◽  
Author(s):  
F Stockmans ◽  
H Deckmyn ◽  
J Gruwez ◽  
J Vermylen ◽  
R Acland
Keyword(s):  
Thrombus Formation ◽  
Femoral Vein ◽  
Maximum Size ◽  
Digital Analysis ◽  
Video Recordings ◽  
Quantitative Monitoring ◽  
Set Up ◽  
Kinetics Of ◽  
Quantitative Nature

SummaryA new in vivo method to study the size and dynamics of a growing mural thrombus was set up in the rat femoral vein. The method uses a standardized crush injury to induce a thrombus, and a newly developed transilluminator combined with digital analysis of video recordings. Thrombi in this model formed rapidly, reaching a maximum size 391 ± 35 sec following injury, after which they degraded with a half-life of 197 ± 31 sec. Histological examination indicated that the thrombi consisted mainly of platelets. The quantitative nature of the transillumination technique was demonstrated by simultaneous measurement of the incorporation of 111In labeled platelets into the thrombus. Thrombus formation, studied at 30 min interval in both femoral veins, showed satisfactory reproducibility overall and within a given animalWith this method we were able to induce a thrombus using a clinically relevant injury and to monitor continuously and reproducibly the kinetics of thrombus formation in a vessel of clinically and surgically relevant size

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