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UV–Vis Spectroscopy of Conjugated Systems01:32

UV–Vis Spectroscopy of Conjugated Systems

Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent of conjugation in the...
UV–Vis Spectrum01:30

UV–Vis Spectrum

When light passes through a substance, a portion of the light is absorbed while the remaining light is reflected or transmitted. If the molecule absorbs light between the wavelengths of 180–400 nm range, the UV spectrum is obtained, and if it absorbs light in the 400–780 nm wavelength range, the visible spectrum is obtained.     
The UV–Vis spectrum of a molecule is the plot of its absorbance versus wavelength. The plot is drawn by taking molar absorptivity (ε) or log ε on the y-axis (ordinate)...
Ultraviolet and Visible (UV–Vis) Spectroscopy: Overview01:02

Ultraviolet and Visible (UV–Vis) Spectroscopy: Overview

Ultraviolet–visible (UV–visible or UV–Vis) spectroscopy is an analytical technique that investigates the interaction between matter and UV–Vis light within the electromagnetic spectrum. This method is widely used for its versatility, simplicity, and relatively quick data acquisition, making it valuable for both qualitative and quantitative analysis. When UV–Vis radiation passes through a material,  molecules absorb light depending on the energy required for electronic transitions. As a result...
UV–Vis Spectrometers01:14

UV–Vis Spectrometers

The absorbance of UV and visible (UV–visible) radiations is measured using a UV–visible spectrophotometer. Deuterium lamps, which emit UV radiation, and tungsten lamps, which produce radiation in the visible region, are used as light sources in UV–visible spectrophotometers. A monochromator or prism is used for diffraction grating, i.e., to split the incoming radiation into different wavelengths. A system of slits is used to focus the desired wavelength on the sample cell. Samples for...
UV–Vis Spectroscopy: Molecular Electronic Transitions01:16

UV–Vis Spectroscopy: Molecular Electronic Transitions

In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this process,...
Photoreceptors and Visual Pathways01:22

Photoreceptors and Visual Pathways

At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...

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Characterization of Biological Absorption Spectra Spanning the Visible to the Short-Wave Infrared
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Published on: January 10, 2025

THE ABSORPTION SPECTRUM OF VISUAL PURPLE.

A M Chase1, C Haig

  • 1Laboratory of Biophysics, Columbia University, New York.

The Journal of General Physiology
|October 30, 2009
PubMed
Summary
This summary is machine-generated.

Researchers optimized visual purple extraction methods to improve light absorption properties. Treatments like alum hardening and pH control enhanced color purity, suggesting chemical interactions and revealing insights into visual purple

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Area of Science:

  • Biochemistry
  • Vision Science
  • Spectrophotometry

Background:

  • Visual purple (rhodopsin) is crucial for vision.
  • Understanding its absorption spectrum is key to visual pigment research.
  • Previous studies established a classical absorption spectrum.

Purpose of the Study:

  • To optimize extraction methods for visual purple.
  • To analyze the factors affecting visual purple purity and stability.
  • To compare extracted spectra with the classical visual purple spectrum.

Main Methods:

  • Extraction of visual purple from retinas using various methods.
  • Measurement of absorption spectra with a photoelectric spectrophotometer.
  • Analysis of effects of alum hardening, extractive concentration, pH, temperature, digitalin treatment, and dialysis.

Main Results:

  • Alum hardening increased light transmission in blue/violet regions.
  • Visual purple solubility is higher than other retinal components.
  • Extractive concentration affected keeping power, not color purity, suggesting chemical binding.
  • Optimal color purity achieved at low pH (5.5-10.0) and higher temperatures (up to 40°C).
  • Digitalin treatment improved purity and keeping power; dialysis caused precipitation.

Conclusions:

  • Optimized extraction techniques can enhance visual purple purity.
  • Factors like pH, temperature, and extractive concentration influence visual purple stability.
  • The classical spectrum likely represents only the light-sensitive group, while extracted spectra reflect the whole molecule.