Spectrophotometry

Question 0

What 3 amino acids absorb light?

Answer 0

Tyrosine, Tryptophan and Phenylalanine

Question 1

What wavelength is the colour red?

Answer 1

~700nm

Question 2

What wavelength does tyrosine absorb light at?

Answer 2

280nm

Question 3

What wavelength do haem groups absorb light at?

Answer 3

400-450nm

550-610nm

Question 4

What wavelength is the colour blue?

Answer 4

~500nm

Question 5

What colour is at the wavelength ~700nm?

Answer 5

Red

Question 6

There were 3 absorption bands at: 430nm, 260nm and 280nm - what three things would these correspond to?

Answer 6

Haem group, Nucleic acids, Tyrosine/Tryptophan/Phenylalanine

Question 8

What light source is used for spectrophotometry between 200-350nm?

Answer 8

deuterium arc source, a halogen source is used for wavelengths above 300nm

Question 9

What is the variation in the beer lambert law accounting for stray light?

Answer 9

Log{(I0 + S)/(I + S)}

This means that as absorbance increases, so does the margin of error from stray light,

Question 10

What colour is at ~400nm?

Answer 10

Violet

Question 11

What wavelength do nucleic acids absorb light at?

Answer 11

260nm

Question 12

In the Beer-Lambert law, what 2 things is absorbance equal to?

Answer 12

Log(I0/I) and e.c.l

Question 13

As the absorbance increases will there be a greater or lesser error from stray light?

Answer 13

Greater error

Question 14

When analysing a mixture of 2 components with the goal of finding each of their concentrations, how should you form the beer-lambert equations?

Answer 14

A = ecl1 + ecl2

Question 15

What colour is at ~500nm?

Answer 15

Blue

Question 16

What is a standard curve used for?

Answer 16

Used for finding concentration, the beer-lambert Law is not necessarily accurate experimentally due to impact of stray light, as absorbance drops below expected value. Standard curves are used

Question 17

What is the Isobestic point used for?

Answer 17

Finding out the total concentration of a mixture of species - cannot discover individual species concentrations from this

Question 18

When analysing a mixture of 2 components, aiming to find the concentrations of both, what 2 values of each species do you require?

Answer 18

Molar extinction coefficient (species must have different coefficients) at 2 different wavelengths

Question 19

At what wavelength is it necessary to Quartz cuvettes?

Answer 19

Wavelengths BELOW 300nm

For longer wavelengths, optical glass may be used

Question 19

At the Isobestic point, what is the same for the 2 species?

Answer 19

When varying wavelength, the Isobestic point is the point at which two species have the same molar extinction coefficient