The preparation of porphyrin S-411 (dehydrocoproporphyrin) and harderoporphyrin from protoporphyrin IX

1981 ◽  
Vol 59 (5) ◽  
pp. 779-785 ◽  
Author(s):  
David Dolphin ◽  
Ramani Sivasothy
Keyword(s):  
Dimethyl Ester ◽  
Protoporphyrin Ix ◽  
The Other ◽  
Side Chain ◽  
Side Chains ◽  
Positional Isomers ◽  
Other Hand ◽  
Hydroxyethyl Group

Protoporphyrin IX dimethyl ester has been converted into the two 2,4-positional isomers bearing hydroxyethyl and methoxycarbonylvinyl side chains. The 4-(2-hydroxyethyl) group was extended to a methoxycarbonylethyl group to give the tetramethyl ester of porphyrin S-411 (2-methoxycarbonylvinyl-4-methoxycarbonylethyldeuteroporphyrin dimethyl ester). On the other hand reduction of the 4-methoxycarbonylvinyl to the corresponding methoxycarbonylethyl group and dehydration of the 2-(2-hydroxyethyl) to a vinyl side chain gave the trimethyl ester of harderoporphyrin (2-vinyl-4-methoxycarbonylethyldeuteroporphyrin dimethyl ester).

Comparison of the Potency of 8-L-Arginine, 8-D-Arginine and 8-D-Homoarginine Vasopressin Analogs with Substituted Phenylalanine in Position 2

1994 ◽  
Vol 59 (6) ◽  
pp. 1439-1450 ◽  
Author(s):  
Miroslava Žertová ◽  
Jiřina Slaninová ◽  
Zdenko Procházka
Keyword(s):  
Amino Acid ◽  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Basic Amino Acid ◽  
The Other ◽  
Side Chain ◽  
Inhibitory Potency ◽  
Phase Synthesis ◽  
Other Hand ◽  
Order Of Magnitude

An analysis of the uterotonic potencies of all analogs having substituted L- or D-tyrosine or -phenylalanine in position 2 and L-arginine, D-arginine or D-homoarginine in position 8 was made. The series of analogs already published was completed by the solid phase synthesis of ten new analogs having L- or D-Phe, L- or D-Phe(2-Et), L- or D-Phe(2,4,6-triMe) or D-Tyr(Me) in position 2 and either L- or D-arginine in position 8. All newly synthesized analogs were found to be uterotonic inhibitors. Deamination increases both the agonistic and antagonistic potency. In the case of phenylalanine analogs the change of configuration from L to D in position 2 enhances the uterotonic inhibition for more than 1 order of magnitude. The L to D change in position 8 enhances the inhibitory potency negligibly. Prolongation of the side chain of the D-basic amino acid in position 8 seems to decrease slightly the inhibitory potency if there is L-substituted amino acid in position 2. On the other hand there is a tendency to the increase of the inhibitory potency if there is D-substituted amino acid in position 2.

The Effect of Lithium Alkoxides on Deprotonizations by Superbases Made from Butyllithium and Potassium tert-Pentoxide

1993 ◽  
Vol 58 (6) ◽  
pp. 1445-1451 ◽  
Author(s):  
Lubomír Lochmann ◽  
Hana Jakubův ◽  
Lambert Brandsma
Keyword(s):  
High Reactivity ◽  
The Other ◽  
Molar Ratio ◽  
Side Chain ◽  
Other Hand

The presence or absence of lithium tert-pentoxide (t-PeOLi) in Superbases, prepared from butyllithium (BuLi) and potasium tert-pentoxide (t-PeOK), affects the metallation rate of toluene only slightly, the rate factors being between 1.0 and 0.3. Thus, lithium alkoxide is not essential for the high reactivity of Superbases. However, the ring-to-side chain metallation ratio is increased in the presence of t-PeOLi. On the other hand, an excess of t-PeOK (molar ratio t-PeOK/BuLi ≥ 3)considerably increases in the rate and yield of the side chain methallation of toluene and suppresses its ring mrtallation. In this way, alkoxides enable some control on regioselectivity in Superbase reactions.

scholarly journals Coenzyme F420-Dependent Glucose-6-Phosphate Dehydrogenase-Coupled Polyglutamylation of Coenzyme F420in Mycobacteria

2018 ◽  
Vol 200 (23) ◽  
Author(s):  
Endang Purwantini ◽  
Usha Loganathan ◽  
Biswarup Mukhopadhyay
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Genetic Analysis ◽  
The Other ◽  
Side Chain ◽  
Side Chains ◽  
Content Type ◽  
Terminal Domain ◽  
Carboxy Terminal Domain ◽  
Carboxy Terminal ◽  
Glucose 6 Phosphate Dehydrogenase

ABSTRACTCoenzyme F420plays a key role in the redox metabolisms of various archaea and bacteria, includingMycobacterium tuberculosis. InM. tuberculosis, F420-dependent reactions have been linked to several virulence factors. F420carries multiple glutamate residues in the side chain, forming F420-nspecies (n, number of glutamate residues), and the length of this side chain impacts cellular physiology.M. tuberculosisstrains with F420species carrying shorter side chains exhibit resistance to delamanid and pretomanid, two new tuberculosis (TB) drugs. Thus, the process of polyglutamylation of F420is of great interest. It has been known from genetic analysis that in mycobacteria an F420-0 γ-glutamyl ligase (FbiB) introduces up to seven glutamate residues into F420. However, purified FbiB ofM. tuberculosis(MtbFbiB) is either inefficient or incapable of incorporating more than two glutamates. We found that,in vitro,MtbFbiB synthesized side chains containing up to seven glutamate residues if F420was presented to the enzyme in a two-electron reduced state (F420H2). Our genetic analysis inMycobacterium bovisBCG andMycobacterium smegmatisand an analysis of literature data onM. tuberculosisrevealed that in these mycobacteria the polyglutamylation process requires the assistance of F420-dependent glucose-6-phosphate dehydrogenase (Fgd) which reduces F420to F420H2. We hypothesize that, starting with F420-0H2, the amino-terminal domain of FbiB builds F420-2H2, which is then transferred to the carboxy-terminal domain for further glutamylation; F420-2H2modifies the carboxy-terminal domain structurally to accommodate longer glutamyl chains. This system is analogous to folylpolyglutamate synthase, which introduces more than one glutamate residue into folate only after this vitamin is reduced to tetrahydrofolate.IMPORTANCECoenzyme F420-dependent reactions ofMycobacterium tuberculosis, which causes tuberculosis, potentially contributes to the virulence of this bacterium. The coenzyme carries a glutamic acid-derived tail, the length of which influences the metabolism ofM. tuberculosis. Mutations that eliminate the production of F420with longer tails makeM. tuberculosisresistant to two new tuberculosis drugs. This report describes that the synthesis of longer glutamyl tails of F420requires concerted actions of two enzymes, one of which reduces the coenzyme prior to the action of the other, which catalyzes polyglutamylation. This knowledge will help to develop more effective tuberculosis (TB) drugs. Remarkably, the introduction of multiple glutamate residues into the sidechain of folate (vitamin B9) requires similar concerted actions, where one enzyme reduces the vitamin to tetrahydrofolate and the other catalyzes polyglutamylation; folate is required for DNA and amino acid synthesis. Thus, the reported research has also revealed a key similarity between two important cellular systems.

scholarly journals Characterization of Chloroquine-Ferriheme Solution Structure Using EXAFS and MD

2014 ◽  
Vol 70 (a1) ◽  
pp. C721-C721
Author(s):  
David Kuter ◽  
Victor Streltsov ◽  
Natalia Davydova ◽  
Gerhard Venter ◽  
Kevin Naidoo ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Solution Structure ◽  
Antimalarial Activity ◽  
Dimethyl Ester ◽  
Protoporphyrin Ix ◽  
Md Simulations ◽  
Exafs Spectrum ◽  
Convincing Evidence ◽  
The Other ◽  
Dimeric Form

The complex formed between the antimalarial drug chloroquine (CQ) and its target iron(III)protoporphyrin IX (ferriheme) in aqueous solution is of considerable importance in understanding its mechanism of antimalarial activity. Recently, convincing evidence showed that CQ induces the μ-oxo dimeric form of ferriheme in aqueous solution, but the structure of this complex in solution is uncertain.[1] Molecular dynamics (MD) simulations in aqueous solution were used to model the structure of μ-oxo ferriheme and two possible conformations of the CQ-ferriheme complex, one in which CQ π-stacked with the unligated face of ferriheme and the other in which CQ was docked between the porphyrin rings. The EXAFS spectrum of μ-oxo ferriheme obtained from frozen solution strongly supported the hydrated structure determined from MD simulation where an excellent fit to the spectrum was only obtained when incorporating waters of hydration at regions identified by computation. On the other hand, the EXAFS spectrum recorded on the dried solid of μ-oxo ferriheme required no solvating waters to produce excellent agreement with the crystal structure of μ-oxo ferrihaem dimethyl ester.[2] The EXAFS spectrum recorded on a frozen aqueous solution of the CQ-ferriheme complex was able to distinguish between the two conformations modeled computationally. Fits to the EXAFS spectrum using the π-stacked structure produced poor agreement while those obtained using the docked conformation reproduced the spectrum well. This indicated that the latter is the most likely form of the CQ-ferriheme complex in aqueous solution.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

Life Beyond 1MeV

1980 ◽  
Vol 38 ◽  
pp. 30-33
Author(s):  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
Past Experience ◽  
The Other ◽  
Good Case ◽  
Other Hand ◽  
The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

Can the Academic Self-Concept be Positive and Realistic?

2005 ◽  
Vol 19 (3) ◽  
pp. 129-132 ◽  
Author(s):  
Reimer Kornmann
Keyword(s):  
Academic Performance ◽  
Opposite Effect ◽  
Self Esteem ◽  
Point Of View ◽  
The Other ◽  
Self Concept ◽  
High Ability ◽  
Self Image ◽  
Other Hand

Summary: My comment is basically restricted to the situation in which less-able students find themselves and refers only to literature in German. From this point of view I am basically able to confirm Marsh's results. It must, however, be said that with less-able pupils the opposite effect can be found: Levels of self-esteem in these pupils are raised, at least temporarily, by separate instruction, academic performance however drops; combined instruction, on the other hand, leads to improved academic performance, while levels of self-esteem drop. Apparently, the positive self-image of less-able pupils who receive separate instruction does not bring about the potential enhancement of academic performance one might expect from high-ability pupils receiving separate instruction. To resolve the dilemma, it is proposed that individual progress in learning be accentuated, and that comparisons with others be dispensed with. This fosters a self-image that can in equal measure be realistic and optimistic.

Stories and the Self

2020 ◽  
Vol 32 (2) ◽  
pp. 47-58 ◽  
Author(s):  
Stefan Krause ◽  
Markus Appel
Keyword(s):  
Meta Analysis ◽  
The Self ◽  
The Other ◽  
Lower Degree ◽  
Contrast Effects ◽  
Self Perception ◽  
Self Perceptions ◽  
Other Hand ◽  
The One ◽  
Implicit And Explicit

Abstract. Two experiments examined the influence of stories on recipients’ self-perceptions. Extending prior theory and research, our focus was on assimilation effects (i.e., changes in self-perception in line with a protagonist’s traits) as well as on contrast effects (i.e., changes in self-perception in contrast to a protagonist’s traits). In Experiment 1 ( N = 113), implicit and explicit conscientiousness were assessed after participants read a story about either a diligent or a negligent student. Moderation analyses showed that highly transported participants and participants with lower counterarguing scores assimilate the depicted traits of a story protagonist, as indicated by explicit, self-reported conscientiousness ratings. Participants, who were more critical toward a story (i.e., higher counterarguing) and with a lower degree of transportation, showed contrast effects. In Experiment 2 ( N = 103), we manipulated transportation and counterarguing, but we could not identify an effect on participants’ self-ascribed level of conscientiousness. A mini meta-analysis across both experiments revealed significant positive overall associations between transportation and counterarguing on the one hand and story-consistent self-reported conscientiousness on the other hand.

Don’t Put Me in This Group

2019 ◽  
Vol 50 (2) ◽  
pp. 80-93
Author(s):  
Jort de Vreeze ◽  
Christina Matschke
Keyword(s):  
Positive Emotions ◽  
Negative Emotions ◽  
Negative Information ◽  
The Self ◽  
The Other ◽  
Other Hand ◽  
Group Memberships

Abstract. Not all group memberships are self-chosen. The current research examines whether assignments to non-preferred groups influence our relationship with the group and our preference for information about the ingroup. It was expected and found that, when people are assigned to non-preferred groups, they perceive the group as different to the self, experience negative emotions about the assignment and in turn disidentify with the group. On the other hand, when people are assigned to preferred groups, they perceive the group as similar to the self, experience positive emotions about the assignment and in turn identify with the group. Finally, disidentification increases a preference for negative information about the ingroup.

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