x*******i
发帖数: 32 | 1 Hello there:
Trytophan fluorescence spectroscopy could be used to analyze whether protein
is compact or open. Ex at 288 nm and em around 320 nm suggests that protein
is compact (trytophan in hydrophobic environment). Em at longer wavelength
suggests an open structure. Also relative fluorescence intensity could tell
something? Anybody know why?
Thanks |
w***e
发帖数: 269 | 2 It is because the emission wavelength of a fluorophore is very much
influenced by the polarity of the micro-environment. A polar medium makes
the emission "red-shifted", meaning longer wavelength, whereas a non-polar
medium makes the emission blue shifted. Tryptophan is a hydrophobic amino
acid. In a folded protein, it is usually buried within the interior of the
protein (hydrophobic core) so that it is in a relatively non-polar
environment. In a completely unfolded protein, Tryptophan is exposed to
aqueous medium so is in a polar environment. If I remember correctly,
emission at 350nm indicates a completely unfolded protein. The intensity of
a fluorophore is also influenced by polarity, but it is not as useful of a
tool to assess folding and structure as emission wavelength since intensity
is concentration-dependent, and also because intensity is easily subjected
to artifacts such as scattering. |
w***e
发帖数: 269 | 3 Part of my master thesis is about fluorescence spectroscopy. Glad to see
that it can be useful. |
x*******i
发帖数: 32 | 4 Thanks! But why the philic environment causes emission red shift?
Bascially we have a protein soluble at room temperature but it precipitates
at cold temperature such as 4 degree. It re-dissolves when temperature
increases. I am thinking about fluorescence spectroscopy to see compactness
or openness of protein with temperature. |
p*****n
发帖数: 981 | 5 总体能量变低就红移，变高就蓝移
蛋白不融你怎么做fluorescence?
precipitates
compactness
【在 x*******i 的大作中提到】
: Thanks! But why the philic environment causes emission red shift?
: Bascially we have a protein soluble at room temperature but it precipitates
: at cold temperature such as 4 degree. It re-dissolves when temperature
: increases. I am thinking about fluorescence spectroscopy to see compactness
: or openness of protein with temperature.
|
w***e
发帖数: 269 | 6 For the first question, that has to do with how fluorescence occurs.
Basically, when excited electrons return to the ground state, some
energy is lost (as heat), and some energy is emitted as photons
(fluorescence). In polar environment, more energy is lost and less is
emitted. For the second question, I think you should look into
differential scanning calorimetry (or other types of calorimetry). That is
a more common technique to study protein folding/unfolding with
temperature changes, which seems to be what you are trying to study.
precipitates
compactness
【在 x*******i 的大作中提到】
: Thanks! But why the philic environment causes emission red shift?
: Bascially we have a protein soluble at room temperature but it precipitates
: at cold temperature such as 4 degree. It re-dissolves when temperature
: increases. I am thinking about fluorescence spectroscopy to see compactness
: or openness of protein with temperature.
|
