Optical (UV-Vis) Spectroscopy

Question 1

Which electrons does UV-Vis interact with?

Answer 1

Valence Electrons

Question 2

What is the wavelength range for UV-Vis?

Answer 2

200 - 700nm

Question 3

What are the THREE types of energy transition?

Answer 3

1. Rotational (microwaves)
2. Vibrational (infrared)
3. Electronic (uv-vis)

Question 4

Which electrons is most absorption spectroscopy of organic compounds based on?

Answer 4

Transitions of n or p electrons to the p* excited state

Question 5

Which transitions does UV-Vis spectroscopy deal with?

Answer 5

So to Sn transitions

Question 6

What is a Chromophore?

Answer 6

Molecular structure which interacts with a photon

Question 7

What is Conjugation in UV-Vis Absorption?

Answer 7

Double bonds separated by single bonds

Question 8

What is the Beer-Lambert Equation?

Answer 8

A = εcl

Question 9

Which amino acids absorb wavelengths above 240nm?

Answer 9

Tyr, Trp, Phe

Question 10

Do non-aromatic amino acids contribute to UV-Vis absorption of proteins?

Answer 10

No

Question 11

Which amino acids cause the protein absorption at 280nm?

Answer 11

Tyr and Trp

Question 12

Which amino acids cause the protein absorption at ~250nm?

Answer 12

Phe and Cys

Question 13

How do NAs affect UV-Vis absorption of proteins?

Answer 13

They interfere and cause a 10+ times higher specific absorption

Question 14

Which amino acids does Bradford Reagent (Coomassie Brilliant Blue G250) bind to?

Answer 14

BASIC:
*Arg
* Lys
* His
AROMATIC:
* Tyr
* Thr
* Phe

Question 15

What causes reduced absorbance in Polynucleotides?

Answer 15

Stacking interactions between bases (hypochromicity)

Question 16

Which biomolecules DO NOT have characteristic UV-Vis Absorption?

Answer 16

• Mono and Oligosaccharides
• Lipids
• Many Metabolites