scholarly journals Proton-pump mechanism in retinal Schiff base: On the molecular structure of the M-state

2005 ◽  
Vol 155 (2) ◽  
pp. 402-405 ◽  
Author(s):  
Ayan Datta ◽  
Swapan K. Pati
Keyword(s):  
Molecular Structure ◽  
Schiff Base ◽  
Proton Pump ◽  
Pump Mechanism

scholarly journals Structural Characterization of Heterodinuclear ZnII-LnIII Complexes (Ln = Pr, Nd) with a Ring-Contracted H2valdien-Derived Schiff Base Ligand

2021 ◽  
Author(s):  
Shabana Noor ◽  
Richard Goddard ◽  
Fehmeeda Khatoon ◽  
Sarvendra Kumar ◽  
Rüdiger W. Seidel
Keyword(s):  
Molecular Structure ◽  
Schiff Base ◽  
Structural Characterization ◽  
Schiff Base Ligand ◽  
Crystal And Molecular Structure ◽  
X Ray ◽  
X Ray Crystallography ◽  
Imidazoline Ring

AbstractSynthesis and structural characterization of two heterodinuclear ZnII-LnIII complexes with the formula [ZnLn(HL)(µ-OAc)(NO3)2(H2O)x(MeOH)1-x]NO3 · n H2O · n MeOH [Ln = Pr (1), Nd (2)] and the crystal and molecular structure of [ZnNd(HL)(µ-OAc)(NO3)2(H2O)] [ZnNd(HL)(OAc)(NO3)2(H2O)](NO3)2 · n H2O · n MeOH (3) are reported. The asymmetrical compartmental ligand (E)-2-(1-(2-((2-hydroxy-3-methoxybenzylidene)amino)-ethyl)imidazolidin-2-yl)-6-methoxyphenol (H2L) is formed from N1,N3-bis(3-methoxysalicylidene)diethylenetriamine (H2valdien) through intramolecular aminal formation, resulting in a peripheral imidazoline ring. The structures of 1–3 were revealed by X-ray crystallography. The smaller ZnII ion occupies the inner N2O2 compartment of the ligand, whereas the larger and more oxophilic LnIII ions are found in the outer O2O2’ site. Graphic Abstract Synthesis and structural characterization of two heterodinuclear ZnII-LnIII complexes (Ln = Pr, Nd) bearing an asymmetrical compartmental ligand formed in situ from N1,N3-bis(3-methoxysalicylidene)diethylenetriamine (H2valdien) through intramolecular aminal formation are reported.

scholarly journals Interactions of Trivalent Lanthanide Cations with a New Hexadentate Di-Schiff Base: New Lanthanide(III) Complexes from (NE,N′E)-2,2′-(ethane-1,2-diylbis(oxy))bis(N-(pyridin-2-ylmethylene)ethanamine)

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Mantha Tsiouri ◽  
Konstantina Skorda ◽  
Christos Papadimitriou ◽  
Yang Li ◽  
J. Derek Woollins ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Schiff Base ◽  
Schiff Base Ligand ◽  
Direct Reaction ◽  
The Novel ◽  
Trivalent Lanthanide ◽  
Lanthanide Cations ◽  
Oxygen Atoms

The novel lanthanide(III) complexes[Ln(NO3)2L](NO3)⋅3MeOH (Ln = La1, Pr2) and[Ln(NO3)3L](NO3)⋅2MeOH (Ln = Gd3, Yb4), where L = (NE,N′E)-2,2′-(ethane-1,2-diylbis(oxy))bis(N-(pyridin-2-ylmethylene)ethanamine), have been obtained by direct reaction of the Schiff base ligand and the corresponding hydrated lanthanide(III) nitrates in methanol. All complexes were characterized spectroscopically and thermogravimetrically. Complex4was also characterized with crystallographic studies: orthorhombic P212121,a=10.6683(14),b=13.4752(15),c=19.3320(26) Å. In the molecular structure of4, Yb(III) is surrounded by all donor atoms of the Schiff base (four nitrogen and two oxygen atoms) and four oxygen atoms belonging to two bidentate chelating nitrato ligands.

scholarly journals Breaking the Carboxyl Rule

2013 ◽  
Vol 288 (29) ◽  
pp. 21254-21265 ◽  
Author(s):  
Sergei P. Balashov ◽  
Lada E. Petrovskaya ◽  
Eleonora S. Imasheva ◽  
Evgeniy P. Lukashev ◽  
Andrei K. Dioumaev ◽  
...  
Keyword(s):  
Schiff Base ◽  
Water Molecule ◽  
Proton Pump ◽  
Rate Constants ◽  
Proton Donor ◽  
Carboxyl Group ◽  
Amino Group ◽  
Wild Type ◽  
Fast Phase ◽  
Proton Uptake

A lysine instead of the usual carboxyl group is in place of the internal proton donor to the retinal Schiff base in the light-driven proton pump of Exiguobacterium sibiricum (ESR). The involvement of this lysine in proton transfer is indicated by the finding that its substitution with alanine or other residues slows reprotonation of the Schiff base (decay of the M intermediate) by more than 2 orders of magnitude. In these mutants, the rate constant of the M decay linearly decreases with a decrease in proton concentration, as expected if reprotonation is limited by the uptake of a proton from the bulk. In wild type ESR, M decay is biphasic, and the rate constants are nearly pH-independent between pH 6 and 9. Proton uptake occurs after M formation but before M decay, which is especially evident in D2O and at high pH. Proton uptake is biphasic; the amplitude of the fast phase decreases with a pKa of 8.5 ± 0.3, which reflects the pKa of the donor during proton uptake. Similarly, the fraction of the faster component of M decay decreases and the slower one increases, with a pKa of 8.1 ± 0.2. The data therefore suggest that the reprotonation of the Schiff base in ESR is preceded by transient protonation of an initially unprotonated donor, which is probably the ϵ-amino group of Lys-96 or a water molecule in its vicinity, and it facilitates proton delivery from the bulk to the reaction center of the protein.

The effects of molecular structure and functional group of a rodlike Schiff base mesogen on blue phase stabilization in a chiral system

2019 ◽  
Vol 43 (4) ◽  
pp. 1743-1756
Author(s):  
Chiung-Cheng Huang ◽  
Yu-Chang Huang ◽  
Wei-Cheng Hsieh ◽  
Yen-Jung Chen ◽  
Shi-Kai Jiang ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Schiff Base ◽  
Functional Group ◽  
Phase Stabilization ◽  
System P ◽  
Blue Phase ◽  
Chiral Dopants ◽  
Chiral System

A wider blue phase (BP) range can be induced easily when two difluoro substituted and racemic rodlike Schiff base mesogens are doped with the appropriate concentration of chiral dopants S811 or ISO(6OBA)2.

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