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When a protein in solution is analyzed using UV-visible, a peak at 280 nm is commonly observed. This peak is due to the effect of aromatic rings in the polypeptide chain (from amino acids tryptophan and tyrosine).
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A diluted protein solution (1 in 100) has an absorbance of 0.558 at 280nm when measured in a 1cm path-length cuvette. Calculate the concentration in mgmL of the undiluted protein solutions (extinctio?
One needs the extinction coefficient in order to answer this question. Otherwise it cannot be answered properly.
Why do you use the wavelength with the maximum absorbance in spectroscopy?
Short answer:Using the maximum wavelength gives us the best results. This is because at the peak absorbance, the absobance strength of light will be at the highest and rate of change in absorbance with wavelength will be the smallest. Measurements made at the peak absorbance will have the smallest error.Long answer: It really depends on what is the largest source of error. Taking the readings at the peak maximum is best at low absorbance, because it gives the best signal-to-noise ratio, which improves the precision of measurement. If the dominant source of noise is photon noise, the precision of absorbance measurement is theoretically best when the absorbance is near 1.0. So if the peak absorbance is below 1.0, then using the peak wavelength is best, but if the peak absorbance is well above 1.0, you might be better off using another wavelength where the absorbance is closer to 1. Another issue is calibration curve non-linearity, which can result in curve-fitting errors. The non-linearity caused by polychromatic light is minimized if you take readings at either a peak maximum or a minimum, because the absorbance change with wavelength is the smallest at those wavelengths. On the other hand, using the maximum increases the calibration curve non-linearity caused by stray light. Very high absorbances cause two problems: the precision of measurement is poor because the transmitted intensity is so low, and the calibration curve linearity is poor due to stray light. The effect of stray light can be reduced by taking the readings at awavelength where the absorbance is lower or by using a non-linear calibration curve fitting technique. Finally, if spectral interferences are a problem, the best measurement wavelength may be the one that minimizes the relative contribution of spectral interferences (which may or may not be the peak maximum). In any case, don't forget: whatever wavelength you use, you have to use the exact same wavelength for all the standards and samples. See http://terpconnect.umd.edu/~toh/models/BeersLaw.htmlTom O'HaverProfessor Emeritus
Would the concentration of a diluted protein shake with an absorbance value of 70mg ml be darker than a protein concentration of 15mg ml?
It would be darker... As the concentration gets stronger, it gets darker.
Why is absorbance plotted instead of percent transmission when following bacterial growth?
Because when we read absorbance, it's the amount of light absorbed by the bacteria itself. Absorbance is directly related to the amount of bacteria. More absorbance = more bacteria.
What is the specific absorbance of aspirin?
If you have a spectrofotometer ( the thing to mesure the absorbance) then play with the setting and use a maximum. this will lay close to your specific absorbance or take the pharmacopea or a MERCK index
Why acetone show absorbance at 280nm?
Because - Mother Nature has told them! (>C=O at ~273nm)
A diluted protein solution (1 in 100) has an absorbance of 0.558 at 280nm when measured in a 1cm path-length cuvette. Calculate the concentration in mgmL of the undiluted protein solutions (extinctio?
One needs the extinction coefficient in order to answer this question. Otherwise it cannot be answered properly.
What wavelength is the peak absorbance of cobalt chloride?
510 nm
How do you find whether given sample is DNA or RNA?
A spectrophotometer can be used to know if a sample is DNA or RNA. DNA has an absorbance maximaat 260nm, whereas RNA has an absorbance maxima at 280nm. By looking at which one of these two wavelengths the sample is more excited, one can determine if the sample is DNA or RNA.
How the absorbance data correlates to the initial protein concentration in ug ml?
The absorbance data correlates to the initial protein concentration in ug ml in one way. It breaks down protein in the stomach by the action of the stomach acid.
What is absorbance vs concentration?
Absorbance refers to a measure of the capacity associated with a substance as regards absorption of light of a specified wavelength. Whenever you plot a graph of absorbance vs. concentration a direct relationship should be produced
Why do you use the wavelength with the maximum absorbance in spectroscopy?
Short answer:Using the maximum wavelength gives us the best results. This is because at the peak absorbance, the absobance strength of light will be at the highest and rate of change in absorbance with wavelength will be the smallest. Measurements made at the peak absorbance will have the smallest error.Long answer: It really depends on what is the largest source of error. Taking the readings at the peak maximum is best at low absorbance, because it gives the best signal-to-noise ratio, which improves the precision of measurement. If the dominant source of noise is photon noise, the precision of absorbance measurement is theoretically best when the absorbance is near 1.0. So if the peak absorbance is below 1.0, then using the peak wavelength is best, but if the peak absorbance is well above 1.0, you might be better off using another wavelength where the absorbance is closer to 1. Another issue is calibration curve non-linearity, which can result in curve-fitting errors. The non-linearity caused by polychromatic light is minimized if you take readings at either a peak maximum or a minimum, because the absorbance change with wavelength is the smallest at those wavelengths. On the other hand, using the maximum increases the calibration curve non-linearity caused by stray light. Very high absorbances cause two problems: the precision of measurement is poor because the transmitted intensity is so low, and the calibration curve linearity is poor due to stray light. The effect of stray light can be reduced by taking the readings at awavelength where the absorbance is lower or by using a non-linear calibration curve fitting technique. Finally, if spectral interferences are a problem, the best measurement wavelength may be the one that minimizes the relative contribution of spectral interferences (which may or may not be the peak maximum). In any case, don't forget: whatever wavelength you use, you have to use the exact same wavelength for all the standards and samples. See http://terpconnect.umd.edu/~toh/models/BeersLaw.htmlTom O'HaverProfessor Emeritus
Is wavelength or absorbance the dependent variable?
"absorbance"Since in the experiment, you probably choose the wavelength, then measure the absorbance (absorption?, the absorbance is the dependent variable.
What is the torque settings for Renault captur wheel nut?
280Nm
What is the purpose of the blank?
Blank Sample in Spectrophotometry is used to measure the absorbance of light without sample. It is subtracted from the total absorbance for measurement of Absorbance from a sample's absorbance.
Would the concentration of a diluted protein shake with an absorbance value of 70mg ml be darker than a protein concentration of 15mg ml?
It would be darker... As the concentration gets stronger, it gets darker.
What is the purpose of blank samples?
Blank Sample in Spectrophotometry is used to measure the absorbance of light without sample. It is subtracted from the total absorbance for measurement of Absorbance from a sample's absorbance.
