Lecture 4

Question 1

What is Tannic Acid?

Answer 1

It is used as a prefixative and enhances electron density of different protein materials

Question 2

What do resins do?

Answer 2

They dehydrate the sample and fix it so that it can be sliced

Question 3

What are the main resins?

Answer 3

Epon-Araldite resin
Epoxy resins
Methacrylates

Question 4

What is Epon-Araldite resin used for?

Answer 4

Highly reactive carbon compounds

Question 5

What are epoxy resins used for?

Answer 5

Unsaturated hydrocarbons

Question 6

What are methacrylates used for?

Answer 6

Better immuno-labelling

Question 7

How is a sample prepared using Carbon grids?

Answer 7

Carbon is evaporated onto mica. This C film is floated off the mica and laid atop a grid. This is heated to 140C for 1-2 hors, this glow discharge makes the carbon briefly hydrophillic

Question 8

How do you carry out heavy metal shadowing?

Answer 8

The sample is chemically fixed/ Machine with a C rod, upon which is a tiny piece of Pt. The pt is evaporated using an electron beam, at an angle to the sample. This creates an uneven distribution. Carbon is them laid atop this.

Question 9

What is heavy metal shadowing useful for?

Answer 9

Seeing cell appendages

Question 10

How do you perform freeze etching?

Answer 10

Concentrated cell suspension is applied onto a gold carrier. This is physically fixed using liquid nitrogen. Inserted into a freeze etch unit in a high vacuum with a temp lower than -100C where the sample is cut witha cold knife. The sample is now etched due to water sublimation. Then use Pt/C shadowing. Float off the PT/C layer with sulphuric acid. This acts like an imprint of the samples.