Protein Surface Interactions

Question 1

What is the time like of protien surface interaction

Answer 1

• proteins arrive at the surface in less than a second
• within seconds/minutes, a protein monolayer is absorbed
• Cells arrive next and see the protein layer and not the biomaterial and the cells interact with the protein layer

Question 2

Why do transplants and biomaterials invoke different responses from the body

Answer 2

transplants have MHC markers which will be slightly different from the hosts MHC which means that the body registers them as foreign and an immune response is invoked. Due to the protein monolayer, cells recognise the biomaterial (with integrins) and won’t attack it

Question 3

What are the 4 principles of protein absorption?

Answer 3

Diffusion, the forces that drive protein absorption, Langmuir model and beyond Langmuir

Question 4

Explain Diffusion as a mechanism for protein absorption?

Answer 4

Proteins are in solution, diffusion means that things will move from low concentration to high concentration. Ficks Law explains how fast proteins will move to the surface. Flux is proportional to the negative of diffusion constant multiplied by the concentration gradient.

Question 5

How does Ficks Law explain that smaller proteins will arrive at the surface faster than larger proteins?

Answer 5

Smaller proteins have a larger diffusion constant than larger proteins. As we are going from high concentration to low the concentration gradient would be negative, so, therefore, the negatives cancel out and would mean that smaller proteins have a larger flux

Question 6

What does the cottrels law state?

Answer 6

the concentration of something with time depends on the diffusion constant and correlates with the surface area of the protein (small ones would arrive faster?

Question 7

What is the strongest surface-protein binding?

Answer 7

Electrostatic forces

Question 8

What are electrostatic forces?

Answer 8

positive and negative poles like magnets

Question 9

What is the middle surface-protein binding?

Answer 9

Hydrogen bonding - if you have enough they can be pretty strong

Question 10

What is the least strong surface-protein binding?

Answer 10

Vanderwaals

Question 11

What is the basic theory of Langmuir?

Answer 11

its a simple model for reversible adsorption, basically stating that once a surface is full no more proteins will bind

Question 12

What is stated in the beyond Langmuir section?

Answer 12

1. Restructuring can happen, so there can be a stepped isotherm
2. It’s possible to have multilayer formation where protiens adhere to each other

Question 13

What does it mean when a protein denatures? What factor influences denaturing?

Answer 13

The protein spreads on the surface and loses its structure.

There is more protein denaturing when a surface is hydrophobic

Question 14

Why might problems arise from absorption of your own proteins?

Answer 14

1. The concentration is different in bulk vs surface
2. There might be a change in reactivity e.g. active site of enzymes might be blocked
3. Denaturing of the protein might make it unrecognisable to cells

Question 15

What factors might affect the surface spreading of proteins?

Answer 15

1. time

2. concentration - less means more spreading, more means less

Question 16

What are the rules of thumb?

Answer 16

1. smaller proteins arrive first
2. larger proteins have a greater affinity to attach
3. charge and distribution of charge on a protein affect absorption
4. less stable proteins denature

Question 17

How do charge and distribution of charge on a protein affect absorption?

Answer 17

proteins have greater surface activity near pH neutral and they don’t just react with the surface but each other
- THIS IS WHAT CAUSES THE EXTRINSIC COMPLEMENT!!

Question 18

What surface properties affect absorption?

Answer 18

1. Geometrical (pores)
2. Chemical
3. Microscopic Scale (alpha and beta phases and grain boundaries)
4. Electrical

Question 19

Why is it hard to predict how a material will react?

Answer 19

1. the complex protein mixture
2. Multiple protein absorption
3. Blood material interaction is complex

Question 20

What is the Vroman effect?

Answer 20

The highest mobility proteins generally arrive first and are later replaced by less mobile proteins that have a higher affinity for the surface.

Question 21

Which protein denominates the initial absorption?

Answer 21

Albumin

Question 22

Which proteins are the most problematic if a lot adhere to a surface?

Answer 22

fibrinogen, Factor XII