LASER PHOTOLYSIS OF RETINAL AND ITS PROTONATED AND UNPROTONATED n‐BUTYLAMINE SCHIFF BASE

Fisher, Michael; Weiss, Karl

doi:10.1111/j.1751-1097.1974.tb06597.x

Cited by 68 publications

(54 citation statements)

References 49 publications

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“…21 We expected, then, that when we looked a t the triplet-triplet absorption ( A, , , 460 nm) and the isomerization signal (at X 380 nm) of R E T in MeOH, the signals would be similar in character to, but with magnitude reduced to about 16% of, those seen for R E T in M C H . While +T for R E T in M C H is 0.5, it is reduced to 0.08 in MeOH.…”

Section: Log [Io(t)/ix(t)l = Lellc1lomentioning

confidence: 95%

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Photoisomerization kinetics of 11-cis-retinal, its Schiff base, and its protonated Schiff base

Menger¹,

Kliger²

1976

J. Am. Chem. Soc.

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These authors observed self-association of a proline-containing tripeptide in dimethyl sulfoxide solution, but not in deuterium oxide at solute concentrations of -0.2 M.(27) We assumed all bond lengths of the proline ring to be 1.52 A, the average of bond lengths found in a number of crystal structures. Four angles are needed to specify a particular conformation.** As before, three contiguous bond angles and a dihedral angle were used for this purpose.'2 (28) (31) Accepting Cavanaugh's values Jgauehe = 2.6 Hz and r/tranr = 13.6 H z ,~' we estimate that the major form of iI consists of 21 % Va. 33% Vb. and 46% Vc. The minor structure is calculated to be a mixture of 2% Va, 24%Vb. and 74 % Vc. Cavanaugh's constants may not be transferable to this system, but probably give population estimates that are qualitatively correct.(32) (a) C. W. Haigh and R.Abstract: Kinetics of the photoisomerization of retinal (RET), a retinylidene Schiff base (SB), and a protonated Schiff base (PSB) have been studied using nanosecond laser photolysis techniques. Two paths of isomerization were observed, one occurring over 10's of nanoseconds and one occurring instantaneously in the time frame of the experiment. Data are presented identifying the former process as being mediated through the triplet state. Isomerization is the net result of a delicate balance between competing processes, and the relative amounts of isomerization via the two paths vary with the compound and with the solvent. A model is presented which allows an adequate and consistent interpretation of the experimental results. The significance of our results to visual pigments is discussed. The protonated Schiff base, which is the closest chemical analogue to rhodopsin we investigated, isomerizes through a singlet mechanism. The extremely rapid rate we observe for this isomerization is consistent with prelumirhodopsin being photogenerated from rhodopsin in picoseconds.

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Section: Log [Io(t)/ix(t)l = Lellc1lomentioning

confidence: 95%

“…21 The picture presented above gives a rather fragmentary view of the isomerization process of the chromophore in visual pigments. They found that $isom = 0.45 f 0.1 when the 1 1-cis-retinal is excited by triplet sensitizers but &om was only 0.004 f 0.001 when the retinal was irradiated directly.…”

mentioning

confidence: 99%

Photoisomerization kinetics of 11-cis-retinal, its Schiff base, and its protonated Schiff base

Menger¹,

Kliger²

1976

J. Am. Chem. Soc.

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“…Moreover when rhodopsin is treated with the unique triplet sensitizer trimethyl-1,2-dioxetane, the protein is denatured and the Chromophore isomerized (42). Since the intersystem crossing yield in PRSB has been shown (14,43) to be beyond the experimental detection limit (< 0.001), a triplet-state model would require that in the pigment the rate of triplet formation increases by at least three orders of magnitude. An additional difficulty arises from the fact that radiationlass transitions from the lowest triplet (T 1 ) to the ground state singlet (S 0 ) are relatively slow processes.…”

Section: Studies Of Model Oompoundsmentioning

confidence: 99%

Cis-trans isomerization in the photochemistry of vision

Rosenfeld¹,

Honig²,

Ottolenghi³

et al. 1977

Pure and Applied Chemistry

177

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-Various models proposed for the primary photoevent in vision are critically discussed. It is concluded that the classical picttire of a single cis-trans isomerizatian step is the only ane which satisfactorily accounts for all the available experimental data. Experiments are performed showing that this process is temperature independent over a range of 200 °C. Photoisomeri zation yie lds for the free protanated Schiff base of 11-cis (and a11-trans) retinal are measured as a fi.Dlctian of the excitation wavelength. In cantrast to the efficient and wavelength independent photobleaching of rhodopsin, the yields of the 11-cis-+-a11-trans isomeri zation of the free Chromophore are sma11, exhibi ting a marked dependence an the excitation wavelength. Potential energy curves for both ground and excited states of rhodopsin are derived from the analysis of the accu1111lated experimental data. In variance with the behavior of model compounds, photoisomerization in the pigment proceeds via the quantitative population of a common, barrierless, therma11y relaxed excited state along the 11·12 torsional coordinate separating the 11-cis (rhodopsin) and a11-trans (bathorhodopsin) configurations. In the ground state, irtteractions with the protein destabilize the a11-trans isomerization product, leading to storage of a significant fractian of the photon's energy in the primary step.

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“…with C ij ¼ X a e i ðk a Þ À e 0 ðk a Þ ½ S aj (6) where C ij is generally called "the C matrix." Equation (5) shows that weighted time profile V i t i (i = 1,…, p) can be represented by a linear combination of populationñ n i ½ " ðñ n i ðt 1 Þ;ñ n i ðt 2 Þ; :::Þ T and the C matrix; this provides us with a method to determine the decay time constants, k i .…”

Section: 42mentioning

confidence: 99%

“…[5]. Since retinal has a high quantum yield of intersystem crossing (0.50-0.61) [6], the T 1 absorption spectra can be recorded by 355 nm excitation to the 1B u + singlet state. In the all-trans isomer, a monotonical rise of the T n ‹ T 1 absorption is seen within 100 ps.…”

mentioning

confidence: 99%

Mechanisms of Cis ‐ Trans Isomerization around the Carbon–Carbon Double Bonds via the Triplet State

Koyama

Kakitani

Nagae

2006

Cis‐trans Isomerization in Biochemistry

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It has been shown that cis-trans isomerization (CTI) around a carbon-carbon double bond takes place not in the singlet state but in the triplet state. Schiff base of retinal is also the case, although protonated Schiff base isomerizes via the singlet state (see Ref.[1] for a review). The lowest-triplet (T 1 ) state can be generated through intersystem crossing in retinoids, and through singlet fission of a particular singlet (1B u -) state in carotenoids [2]. Since the quantum yield of triplet generation is generally lower in carotenoids (~10 -3 ), a triplet sensitizer is necessary to study CTI via the T 1 state.The excited-state properties of retinoids and carotenoids have been reviewed, together with chlorophylls, in relation to their biological functions [1]. In the present review, we will briefly summarize the previous results concerning polyenes (Sections 3.2.1 and 3.3.1), and add most recent results along these lines (Sections 3.2.2 and 3.2.3, and 3.3.2-3.3.4), focussing on a retinoid (retinal) and two carotenoids (b-carotene and spheroidene).In accord with the purpose of this book, to provide detailed and critical reviews of most recent highlights, we have tried to incorporate as much data as possible so that they can tell stories by themselves. We hope readers will enjoy reading the figures and tables as well. A Concept of a Triplet-Excited RegionThe concept of a "triplet-excited region" emerged during studies on Raman spectra and isomerization of retinoids and carotenoids in the T 1 state (see Ref.[3] for a summary). The triplet-excited region was defined as a region where large changes in bond order take place toward its inversion upon the ground (S 0 ) to T 1 transition; that is, a double bond becomes more single bond-like and a single bond becomes more double bond-like. It has a span of approximately six conjugated double bonds, it is located in the central part of a conjugated chain, and it triggers CTI. This is a basic concept in understanding the isomerization properties of polycis-trans Isomerization in Biochemistry. Edited by Christophe Dugave

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LASER PHOTOLYSIS OF RETINAL AND ITS PROTONATED AND UNPROTONATED n‐BUTYLAMINE SCHIFF BASE

Cited by 68 publications

References 49 publications

Photoisomerization kinetics of 11-cis-retinal, its Schiff base, and its protonated Schiff base

Photoisomerization kinetics of 11-cis-retinal, its Schiff base, and its protonated Schiff base

Cis-trans isomerization in the photochemistry of vision

Mechanisms of Cis ‐ Trans Isomerization around the Carbon–Carbon Double Bonds via the Triplet State

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