Imines, acids and bases

Question 1

What is the green fluorescent protein isolated from?

Answer 1

The pacific JellyfishL Aequoria Victoria

Question 2

Tell me about the structure of the GFP?

Answer 2

• 238 amino acids
• Beta sheets are present (green)
• Alpha helices are present (blue)
• There are connecting loops between the alpha and beta sheets (yellow)

Question 3

Whats the general structure of an imine?

Answer 3

Question 4

Write the reactions for the formation of Imines when an aldehyde/ Ketone react with a promary amine ?

Answer 4

Question 5

Whats necessary to drive the reaction of the formation of an amine in a lab?

Answer 5

the removal of water

Question 6

What type of reaction is the the reverse of imine formation?

Answer 6

Dehydration

Question 7

Comeplete the following reaction;

Answer 7

Question 8

Draw the overall mechanism of imine formation

Answer 8

Question 9

The mechanism for the formation of imine is split into 2 parts, write out the first part (hemiacetal formation)

include; structures, intermediates

Answer 9

Question 10

Compare hemiaminal formation with hemiacetal formation

Answer 10

Question 11

Write the reaction for the second part of imine formation (onto the imine)

include; structures, intermediates

Answer 11

Question 12

Draw the reaction for an aldehyde/ ketone reacting with a secondary amine.

What is the name of the product formed as well

Answer 12

Question 13

Draw the reaction mechanism for when an aldehyde/ketone reacts with a secondary amine

Answer 13

Question 14

What is this structure?

Answer 14

Question 15

What can imines be formed from?

Answer 15

from pyridoxal phosphate as the aldehyde component

Question 16

Tell me the steps to how the release of Ca2+ from Aequoria leads to it fluorescing

Answer 16

1. The calcium ions bind to a protein called aequorin which releases blue light upon calcium binding. The blue light is absorbed by green fluorescent protein which in turn gives off green light.
2. The part of a molecular structure which absorbs light and re-emits at longer wavelength is called the fluorophore.
3. The GFP fluorophore is derived from a group of three amino acids found in the center of the barrel: Ser65, Tyr66, Gly67
4. The reaction which causes this triplet of amino acids to fluoresce is very closely related to imine/enamine formation.

Question 17

Draw the structure of the 3 amino acids joined together at the centre of the barrell of the GFP?

Answer 17

Question 18

How have a number of fluorescent proteins now been developed?

Answer 18

using protein mutagenesis

Question 19

How can the emission wavelength (colour) be tailored?

Answer 19

by changing the amino acid residues located near the tripeptide fluorophore

Question 20

How is the strength of a Brønsted acid defined?

include a reaction

Answer 20

By how well it transfers H+ to H2O

Question 21

Whats the eqaution for the equilibrium constant?

Answer 21

Question 22

Whats the strong acids dissociation formula?

Answer 22

Question 23

What has a smaller PKa, strong or weak acids ?

Answer 23

stronger acids

Question 24

A table to show substances, their structure, PKa values

Answer 24

Question 25

Whats a Brønsted base and write an equation to show this?

Answer 25

A Brønsted base is a species which accepts H+ in a reaction

Question 26

What is the strength of a Brønsted base related to?

Write an equation to support this?

Answer 26

The strength of a Brønsted base is related to the strength of its conjugate acid i.e. consider the acid dissoctiation equilibrium for BH+

Question 27

If BH+ is a weak acid (its PKa is high) this equilibrium lies to which direction?

What does this correspond to?

Answer 27

Question 28

Write the acid dissociation formula for Brønsted bases?

Answer 28

Question 29

In a reaction between a Brønsted acid and base, what can we calculate and how?

Answer 29

We can calculate the position of the equilibrium by comparing the PKa vlaues of the two acids involved