The photochemistry of vision

Wald, George

doi:10.1007/bf00162600

Cited by 149 publications

(62 citation statements)

References 54 publications

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“…Since workers prior to Lythgoe did not control the pH of their solutions, the interpretation of some of the earlier work is difficult and, to this extent, Wald's strictures on 'difference spectra' are justified (Wald, 1938(Wald, , 1949. Wald has presented a large proportion of his results in the form of absorption spectra of whole retinal extracts, i.e.…”

Section: Discussionmentioning

confidence: 99%

“…Wald (1949) has criticized this figure as an artifact due to their measurement of difference spectra, viz. the difference in absorption between unbleached and bleached solutions.…”

Section: Discussionmentioning

confidence: 99%

“…It is possible that the chromophore parts of the molecules are successive members of a homologous series. It has, in fact, already been suggested that the visual purple and visual violet chromophores are based respectively on vitamin A1 and vitamin A2 (Wald, 1939(Wald, , 1949 For the same reasons the red-insensitive pigment is considered to be a visual pigment. Proof of this must, however, await the demonstration of retinal or behavioural activity in the tench in conformity with the presence of this substance in its retina.…”

Section: Visual Pigment 467mentioning

confidence: 99%

“…He has, however, recorded activity of the frog's retina in this spectral region and the sensitivity/wave-length curve found (Granit, 1943) is in fair agreement, both as regards shape and position of maximum, with that for the red-insensitive pigment. Nomenclature The term 'visual purple' is an equivocal translation of 'Sehpurpur' (Wald, 1949). Solutions of visual purple as ordinarily prepared are red.…”

Section: Visual Pigment 467mentioning

confidence: 99%

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Visual pigment 467, a photosensitive pigment present in tench retinae

Dartnall¹

1952

The Journal of Physiology

125

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Section: Discussionmentioning

confidence: 99%

“…Wald (1949) has criticized this figure as an artifact due to their measurement of difference spectra, viz. the difference in absorption between unbleached and bleached solutions.…”

Section: Discussionmentioning

confidence: 99%

Section: Visual Pigment 467mentioning

confidence: 99%

Section: Visual Pigment 467mentioning

confidence: 99%

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Visual pigment 467, a photosensitive pigment present in tench retinae

Dartnall¹

1952

The Journal of Physiology

125

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“…On irradiation, light absorbed in the a-band or the/3-band causes them both to disappear and the retinenel spectrum with a maximum at 385 m/z finally takes their place (see Fig. 1 in Wald, 1949). The ~/-band does not change on irradiation, and there is someevidence that light absorbed in it is not available for bleaching (Goodeve, Lythgoe, and Schneider, 1941-42).…”

Section: Temperature Dependence Of the Bleaching Ratementioning

confidence: 99%

The Interplay of Light and Heat in Bleaching Rhodopsin

George

1952

Journal of General Physiology

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I mTRODVCTIONThe absorption of light by rhodopsin in the retina activates the pigment molecules and leads eventually to the stimulation of rod vision. The initial light reaction is followed by a sequence of thermal reactions occurring equally in light or darkness, by which the rhodopsin, a conjugated carotenoid protein, ultimately bleaches to retinenel and protein (Wald, Durell, and St. George, 1950). The work described here deals with the initial activation of rhodopsin.Rhodopsin can be bleached not only by light but by heat. At 50°C. or above it bleaches rapidly in the dark and at a rate that is very temperature-dependent. Lythgoe and Quilliam (1938) calculated an experimental activation energy of 44 kg. cal. per mole from their data on the temperature coefficient in neutral solutions. On the other hand, the rate of bleaching by white light is not temperature-dependent, showing that no thermal activation is needed (Hecht, 1920-21).The purpose of the following research was to study the transition between photic and thermal activation. The argument runs as follows. On going from shorter wave lengths to red light a point should be reached beyond which the incident quanta cannot supply the entire energy needed to activate the rhodopsin molecule. If bleaching is to occur nonetheless, the deficit will have to be met by a contribution of thermal energy from the internal degrees of freedom of the molecule. There should therefore be a critical wave length beyond which the bleaching by light becomes temperature-dependent.Measurement of the temperature coefficient of bleaching at intervals along the wave length scale showed that a temperature dependence does in fact appear in the orange at about 590 mu. Moreover, the quantum energy at this wave length differs very little from the activation energy observed in heat bleaching. At wave lengths longer than 590 mt~, the temperature coefficient increases regularly so that the sum of the energy of the absorbed quanta and the thermal ac-

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Physiologic Chemistry of the Eye

Kinsey¹

1950

AMA Arch Ophthalmol

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The photochemistry of vision

Cited by 149 publications

References 54 publications

Visual pigment 467, a photosensitive pigment present in tench retinae

Visual pigment 467, a photosensitive pigment present in tench retinae

The Interplay of Light and Heat in Bleaching Rhodopsin

Physiologic Chemistry of the Eye

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