Questions tagged [spectroscopy]
Questions relating to how biological systems interact with electromagnetic radiation.
22
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How do we see the violet color?
Here is exactly the same question with an accepted answer. However, that answer looks wrong (I can’t find the “alert moderators” button). Firstly, it refers to a dubious source. Secondly, it ...
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What wavelength of light should I use to measure the absorbance of an anabaena population?
I am trying to use a spectrophotometer/colorimeter to measure the relative amounts of anabaena (cyanobacteria) in different samples.
What wavelength should I use to get the maximum absorbance?
4
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Spectroscopic methods for quantifying peptides/proteins with or without Tryptophan or Tyrosine content
I have several peptides (20-50 amino acids long) which I want to quantify the solubility/concentration in a solvent at certain temperature and pH.
These peptides may or may not contain Tryptophan or ...
9
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1
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Why is there a λ⁴ in the spectral overlap integral in FRET calculations
The Förster resonance energy transfer (FRET) spectral overlap integral looks like:
$$
J=\int_{0}^{\infty}\bar{F}_{D}(λ)ε_{A}(λ)λ^4 dλ
$$
Where $λ$ is the wavelength, $\bar{F}_{D}(λ)$ is the normalized ...
2
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1
answer
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Identifying substance in body fluid (serum, urine)
I have a large number of serum and 24 hour urine samples from a collection of individuals on many consecutive days. Some of the samples contain a 'large' amount of a substance that has a brown color. ...
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0
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What is the purpose of putting multiple blanks on a microplate reader? [closed]
I am new to biology and I saw that in the software that controls the microplate reader several targets are set, what is the purpose of this?
4
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1
answer
2k
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Why does absorption (at 260nm) of ssDNA increase with temperature?
In the graph below, I understand why A260 of double stranded DNA would increase with temperature increase, as more of the DNA becomes single stranded (and A260 of ssDNA is higher than that of dsDNA ...
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1
answer
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CD spectra of Porin molecules?
Can anyone please help me how will the CD spectra or graph of porin molecule look like. Porin molecule has 14 beta plated structures joined by some random coil, but it's very confusing to draw it. Can ...
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1
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201
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What happens to the absorbed blue and red light in the chlorophyll molecule?
If the chlorophyll molecule (its chromophore) absorbs red and blue light and reflects green light, shouldn't the absorbed blue and red light be emitted back when its excited electrons relax?
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344
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How do carbon 13:12 ratios confirm the biological origin of oldest microfossils?
I was reading this article about how Schopf and Valley’s findings in 2017 confirmed that the 3.5 billion–year-old microfossils found in the Apex chert of Western Australia are indeed remnants of ...
2
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113
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What does the spectrum of Chlorophyll fluorescence look like?
I've just posted the question Which spacecraft can see plants "glow" during photosynthesis during the day, and what wavelength does it use? in a different SE site. I can't remember the details of ...
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What absorbs light at 380 nm in a sample of DNA oligonucleotide extracted from a PAGE gel?
I have extracted DNA oligonucleotide of size 77 bp from a crushed 10% PAGE gel using 3 rounds of $\ce{LiClO4}$ in water. The extracted elute was dried down in a vacuum centrifuge to a certain volume ...
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727
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Using nanodrop for analysing biological samples other than nucleotides
I am a 3rd timer postdoctoral fellow with some experience in molecular biology and biochemistry, but major skills in Zoology and Natural History. I am studying some natural extracts, and isolating ...
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Why do most plants reflect green and others other colors?
I have read that chlorophyll absorbs red and blue.
As shown in detail in the absorption spectra, chlorophyll absorbs light in the red (long wavelength) and the blue (short wavelength) regions of ...
4
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If you measure the O.D. of cells at one wavelength, is it possible to find its equivalent O.D. at another wavelength?
For example, I measured the optical density (O.D.) of some cells at wavelength 550 nm but I should have used 600 nm. Is there a way of converting my O.D. to its equivalent in another wavelength?
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What will CD spectroscopy show when L- and D- forms of proteins are mixed?
What will happen if equimolar concentration of L- and D- forms of proteins are mixed and we take the circular dichroism reading? Will the positive and negative ellipticity cancel each other out or ...
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How can I calculate alpha helix content from molar ellipticity?
How can I calculate the alpha helix content (i.e. percent) in a protein from a given molar ellipticity of 222 nm, without using any software. I have tried the Greenfield-Fasman equation, but the ...
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Spectroscopy on plant leafs
I'm trying to do spectroscopy readings on plants where I shoot electromagnetic waves and look at their signature/profile.
I want to be able to do this at a distance, in the field and on live plants ...
1
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1
answer
88
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Is galvinoxyl antioxidant assay possible using NMR spectroscopy?
I would like to perform an antioxidant assay using the galvinoxyl protocol. The protocol states that we need EPR spectroscopy, but only NMR spectroscopy is available at my institution. Is there an ...
3
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1
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NMR spectroscopy detection methods for proteins
I've stumbled upon a table comparing the sensitivities of different detection methods in NMR spectroscopy: "Direct", "DEPT" and "Inverse", where "Inverse" seems to be the most sensitive.
What exactly ...
7
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1
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248
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RMSD during conformational transition in proteins
When I was investigating the differences between protein structures obtained by X-ray crystallography and NMR spectroscopy, I found the paper [1] compairing structures of several proteins resolved ...
7
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What is a good non-fluorescent DNA dye?
Can anyone suggest a dye which specifically targets DNA, but is not fluorescent? We plan to mark DNA before observing it with RAMAN-Spectroscopy. Because of the weak signal, even a low emission would ...