scholarly journals Femtochemistry of Rhodopsins

2021 ◽  
Vol 15 (2) ◽  
pp. 344-351
Author(s):  
M. A. Ostrovsky ◽  
V. A. Nadtochenko
Keyword(s):  
Photochemical Reactions ◽  
Halobacterium Salinarum ◽  
High Rate ◽  
Quantum Yields ◽  
Type I ◽  
Type Ii ◽  
Information Process ◽  
Photochromic Reaction ◽  
Protein Environment ◽  
Visual Rhodopsin

Abstract The review considers the spectral kinetic data obtained by us by femtosecond absorption laser spectroscopy for the photochromic reaction of retinal isomerization in animal rhodopsin (type II), namely, bovine visual rhodopsin and microbial rhodopsins (type I), such as Exiguobacterium sibiricum rhodopsin and Halobacterium salinarum bacteriorhodopsin. It is shown that the elementary act of the photoreaction of retinal isomerization in type I and type II rhodopsins can be interpreted as a transition through a conical intersection with retention of the coherence of the vibrational wave packets generated during excitation. The coherent nature of the reaction is most pronounced in visual rhodopsin as a result of the barrier-free movement along the excited surface of potential energy, which also leads to an extremely high rate of retinal isomerization compared to microbial rhodopsins. Differences in the dynamics of photochemical reactions of type I and type II rhodopsins can be related to both differences in the initial isomeric forms of their chromophores (all-trans and 11-cis retinal, respectively), as well as with the effect of the protein environment on the chromophore. Despite the practically identical values of the quantum yields of the direct photoreaction of visual rhodopsin and bacteriorhodopsin, the reverse photoreaction of visual rhodopsin is much less effective (φ = 0.15) than in the case of bacteriorhodopsin (φ = 0.81). It can be assumed that the photobiological mechanism for converting light into an information process in the evolutionarily younger visual rhodopsins (type II rhodopsins) should be more reliable than the mechanism for converting light into a photoenergetic process in the evolutionarily more ancient microbial rhodopsins (type I rhodopsins). The low value of the quantum yield of the reverse reaction of visual rhodopsin can be considered as an increase in the reliability of the forward reaction, which triggers the process of phototransduction.

Molecular photochemistry. XLVIII. Type I and type II photochemical reactions of some five- and six-membered cycloalkanones

1971 ◽  
Vol 93 (26) ◽  
pp. 7213-7221 ◽  
Author(s):  
J. C. Dalton ◽  
K. Dawes ◽  
N. J. Turro ◽  
D. S. Weiss ◽  
J. A. Barltrop ◽  
...  
Keyword(s):  
Photochemical Reactions ◽  
Type I ◽  
Type Ii

scholarly journals Competition Between Cyclization and Unusual Norrish Type I and Type II Nitro-Acyl Migration Pathways in the Photouncaging of 1-Acyl-7-nitroindoline Revealed by Computations

2020 ◽  
Author(s):  
Pierpaolo Morgante ◽  
Charitha Guruge ◽  
Yannick P. Ouedraogo ◽  
Nasri Nesnas ◽  
Roberto Peverati
Keyword(s):  
Density Functional ◽  
Acyl Migration ◽  
Density Functional Theory Calculations ◽  
Computational Procedure ◽  
Quantum Yields ◽  
Type I ◽  
Type Ii ◽  
Relative Quantum ◽  
Norrish Type ◽  
Migration Pathways

The 7-nitroindolinyl family of caging chromophores has received much attention in the past two decades. However, its uncaging mechanism is still not clearly understood. In this study, we performed state-of-the-art density functional theory calculations to unravel the photo-uncaging mechanism in its entirety, and we compared the probabilities of all plausible pathways. We found competition between a classical cyclization and acyl migration pathways, and here we explain the electronic and steric reasons behind such competition. The migration mechanism possesses the characteristics of a combined Norrish Type I and a 1,6-nitro-acyl variation of a Norrish Type II mechanism, which is reported here for the first time. We also introduced a computational procedure that allows the estimation of intersystem crossing rate constants useful to compare the relative quantum yield of substituted cages. This procedure may pave the way for improved cage designs that possess higher quantum yields and a more efficient agonist release.<br>

Modification of photochemical reactivity through the use of clathrates: the Norrish type I and type II reactions in Dianin's compound

1985 ◽  
Vol 63 (10) ◽  
pp. 2719-2725 ◽  
Author(s):  
P. C. Goswami ◽  
Paul de Mayo ◽  
N. Ramnath ◽  
G. Bernard ◽  
N. Omkaram ◽  
...  
Keyword(s):  
Inclusion Complexes ◽  
Hydrogen Abstraction ◽  
Photochemical Reactions ◽  
Type I ◽  
Type Ii ◽  
Guest Molecules ◽  
Photochemical Reactivity ◽  
Norrish Type ◽  
Restricted Environment ◽  
Dianin's Compound

Dianin's compound (4-p-hydroxyphenyl-2,2,4-trimethylchroman) serves as host in a series of well-defined clathrate inclusion complexes with eleven linear, as well as branched chain, phenyl alkyl ketone guest molecules, chosen for their ability to undergo the Norrish type I and type II photochemical reactions in solution. The photochemical reactivity of the guest ketones within the clathrate cavity was determined by irradiation of the inclusion complexes in the solid state. The results were compared to the photoreactivity of the ketones in polar as well as nonpolar liquid media. In general, the inclusion complex medium brings about an enhancement of type I over type II reactivity and causes an increase in type II fragmentation compared to type II cyclization. This change in reactivity is interpreted as resulting from the relatively restricted environment of the clathrate cavity coupled with the greater motion required for the type II process (γ-hydrogen abstraction) compared to the type I reaction (α-cleavage), as well as from the greater steric requirements for type II cyclization (cyclobutanol formation) as compared to type II cleavage (1,4-hydroxybiradical scission).

scholarly journals The Study of a 231 French Patient Cohort Significantly Extends the Mutational Spectrum of the Two Major Usher Genes MYO7A and USH2A

2021 ◽  
Vol 22 (24) ◽  
pp. 13294
Author(s):  
Luke Mansard ◽  
David Baux ◽  
Christel Vaché ◽  
Catherine Blanchet ◽  
Isabelle Meunier ◽  
...  
Keyword(s):  
Massively Parallel Sequencing ◽  
Splice Variants ◽  
Usher Syndrome ◽  
Genetic Diagnosis ◽  
Autosomal Recessive Disorder ◽  
Severe Form ◽  
High Rate ◽  
Type I ◽  
Type Ii ◽  
Causal Genes

Usher syndrome is an autosomal recessive disorder characterized by congenital hearing loss combined with retinitis pigmentosa, and in some cases, vestibular areflexia. Three clinical subtypes are distinguished, and MYO7A and USH2A represent the two major causal genes involved in Usher type I, the most severe form, and type II, the most frequent form, respectively. Massively parallel sequencing was performed on a cohort of patients in the context of a molecular diagnosis to confirm clinical suspicion of Usher syndrome. We report here 231 pathogenic MYO7A and USH2A genotypes identified in 73 Usher type I and 158 Usher type II patients. Furthermore, we present the ACMG classification of the variants, which comprise all types. Among them, 68 have not been previously reported in the literature, including 12 missense and 16 splice variants. We also report a new deep intronic variant in USH2A. Despite the important number of molecular studies published on these two genes, we show that during the course of routine genetic diagnosis, undescribed variants continue to be identified at a high rate. This is particularly pertinent in the current era, where therapeutic strategies based on DNA or RNA technologies are being developed.

scholarly journals Competition Between Cyclization and Unusual Norrish Type I and Type II Nitro-Acyl Migration Pathways in the Photouncaging of 1-Acyl-7-nitroindoline Revealed by Computations

2020 ◽  
Author(s):  
Pierpaolo Morgante ◽  
Charitha Guruge ◽  
Yannick P. Ouedraogo ◽  
Nasri Nesnas ◽  
Roberto Peverati
Keyword(s):  
Density Functional ◽  
Acyl Migration ◽  
Density Functional Theory Calculations ◽  
Computational Procedure ◽  
Quantum Yields ◽  
Type I ◽  
Type Ii ◽  
Relative Quantum ◽  
Norrish Type ◽  
Migration Pathways

The 7-nitroindolinyl family of caging chromophores has received much attention in the past two decades. However, its uncaging mechanism is still not clearly understood. In this study, we performed state-of-the-art density functional theory calculations to unravel the photo-uncaging mechanism in its entirety, and we compared the probabilities of all plausible pathways. We found competition between a classical cyclization and acyl migration pathways, and here we explain the electronic and steric reasons behind such competition. The migration mechanism possesses the characteristics of a combined Norrish Type I and a 1,6-nitro-acyl variation of a Norrish Type II mechanism, which is reported here for the first time. We also introduced a computational procedure that allows the estimation of intersystem crossing rate constants useful to compare the relative quantum yield of substituted cages. This procedure may pave the way for improved cage designs that possess higher quantum yields and a more efficient agonist release.<br>

scholarly journals Competition between cyclization and unusual Norrish type I and type II nitro-acyl migration pathways in the photouncaging of 1-acyl-7-nitroindoline revealed by computations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Pierpaolo Morgante ◽  
Charitha Guruge ◽  
Yannick P. Ouedraogo ◽  
Nasri Nesnas ◽  
Roberto Peverati
Keyword(s):  
Density Functional ◽  
Acyl Migration ◽  
Density Functional Theory Calculations ◽  
Quantum Yields ◽  
Type I ◽  
Type Ii ◽  
Migration Pathway ◽  
Norrish Type ◽  
Triplet Excited States ◽  
Migration Pathways

AbstractThe 7-nitroindolinyl family of caging chromophores has received much attention in the past two decades. However, its uncaging mechanism is still not clearly understood. In this study, we performed state-of-the-art density functional theory calculations to unravel the photo-uncaging mechanism in its entirety, and we compared the probabilities of all plausible pathways. We found competition between a classical cyclization and an acyl migration pathway, and here we explain the electronic and steric reasons behind such competition. The migration mechanism possesses the characteristics of a combined Norrish type I and a 1,6-nitro-acyl variation of a Norrish type II mechanism, which is reported here for the first time. We also found negligible energetic differences in the uncaging mechanisms of the 4-methoxy-5,7-dinitroindolinyl (MDNI) cages and their mononitro analogues (MNI). We traced the experimentally observed improved quantum yields of MDNI to a higher population of the reactants in the triplet surface. This fact is supported by a more favorable intersystem crossing due to the availability of a higher number of triplet excited states with the correct symmetry in MDNI than in MNI. Our findings may pave the way for improved cage designs that possess higher quantum yields and a more efficient agonist release.

The use of Ellis pins (negative profile tip-threaded pins) in external skeletal fixation in dogs and cats

2003 ◽  
Vol 16 (04) ◽  
pp. 223-231 ◽  
Author(s):  
M. J. Pead ◽  
A. L. Beck
Keyword(s):  
High Rate ◽  
Type I ◽  
Type Ii ◽  
Chi Square ◽  
Exact Test ◽  
Risk Of Failure ◽  
Fisher’S Exact Test ◽  
Chi Square Test ◽  
Rate Of Failure

SummaryThe Ellis pin is commonly used in external skeletal fixators (ESFs) but some authors suggest that this pin suffers from a high rate of failure. The purpose of this study was to look for complications associated with four different pin types, in particular pin breakage, as well as pin loosening, radiolucency around pins and pin tract discharge. Fifty consecutive cases which had an ESF applied using Ellis pins were identified. Radiographs and case records were used to record case details, ESF design, duration of fixation, pin types used, and complications. Records from 31 dogs and 17 cats were examined (2 animals were removed from the study because of incomplete follow-up). There were 21 Type I, 7 Type I with a tied-in IM pin, 2 modified Type I, 2 modified Type I with a tied-in IM pin and 16 modified Type II ESFs. 160 Ellis pins, 30 centrally threaded positive profile pins, 4 end threaded positive profile pins and 46 smooth pins were used. Complications relating to one or more of the pins were seen in 65% of the fixators. None of the pins broke. There was a significant association between individual pin type and the number of pins showing loosening (p = 0.002) or radiolucency (p = 0.006), but not a significance in the association between pin type and discharge (Chi-Square test). When each pin was compared against each other pin, smooth pins were significantly more likely to be loose than Ellis pins (p <0.001), and centrally threaded positive profile pins were significantly more likely to result in radiolucency than Ellis pins (p = 0.01), using a Chi-square test. There was not any significant association between any other pin types for any complication using a Fisher’s Exact test. The study demonstrates that Ellis pins, when inserted correctly, are not at any greater risk of failure than other pin types, and that fewer complications may be associated with them than other pin designs.

scholarly journals Competition Between Cyclization and Unusual Norrish Type I and Type II Nitro-Acyl Migration Pathways in the Photouncaging of 1-Acyl-7-nitroindoline Revealed by Computations

2020 ◽  
Author(s):  
Pierpaolo Morgante ◽  
Charitha Guruge ◽  
Yannick P. Ouedraogo ◽  
Nasri Nesnas ◽  
Roberto Peverati
Keyword(s):  
Density Functional ◽  
Acyl Migration ◽  
Density Functional Theory Calculations ◽  
Computational Procedure ◽  
Quantum Yields ◽  
Type I ◽  
Type Ii ◽  
Relative Quantum ◽  
Norrish Type ◽  
Migration Pathways

The 7-nitroindolinyl family of caging chromophores has received much attention in the past two decades. However, its uncaging mechanism is still not clearly understood. In this study, we performed state-of-the-art density functional theory calculations to unravel the photo-uncaging mechanism in its entirety, and we compared the probabilities of all plausible pathways. We found competition between a classical cyclization and acyl migration pathways, and here we explain the electronic and steric reasons behind such competition. The migration mechanism possesses the characteristics of a combined Norrish Type I and a 1,6-nitro-acyl variation of a Norrish Type II mechanism, which is reported here for the first time. We also introduced a computational procedure that allows the estimation of intersystem crossing rate constants useful to compare the relative quantum yield of substituted cages. This procedure may pave the way for improved cage designs that possess higher quantum yields and a more efficient agonist release.<br>

Photochemistry of Ketones in Carbon Tetrachloride Solution

1973 ◽  
Vol 51 (9) ◽  
pp. 1435-1440 ◽  
Author(s):  
J. O. Pavlik ◽  
P. I. Plooard ◽  
A. C. Somersall ◽  
J. E. Guillet
Keyword(s):  
Energy Transfer ◽  
Carbon Tetrachloride ◽  
Quantum Yields ◽  
Type I ◽  
Type Ii ◽  
Definitive Evidence ◽  
Carbon Tetrachloride Solution ◽  
Radiationless Energy Transfer ◽  
Norrish Type ◽  
Low Efficiency

Acetone, chloroacetone, 4-heptanone, 8-pentadecanone, 12-tricosanone, and dimethyl γ-keto pimellate were photolyzed at 3130 Å in carbon tetrachloride solution. The quantum yields of C2Cl6 formed, the decrease in Norrish type I and type II products, the copious yields of HCl and the Stern–Volmer quenching of ketone fluorescence by carbon tetrachloride provide definitive evidence for energy transfer which is rationalized by an exciplex mechanism of low efficiency. The excited [n,π*]1 state of the ketone forms a loose complex with the CCl4 and radiationless energy transfer leads to dissociation of the CCl4 in the primary chemical step.

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