The rate at which particles of size d1 and d2 contact each other by the jth transport mechanism is given by the following equation: ; where  is the collision frequency function for the jth transport mechanism (i.e., perikinetic, orthokinetic, or differential settling). Plot log as a function of log for d1=1 um, T= 298 oK, , and a velocity gradient of 10/sec. What are your conclusions based on this graph?

(Calculate  for d2=0.01, 0.1, 1, 10 and 100 um in order to construct the graph).

What are prions?

In cell, there are subcellular organelles. They are not full organism. Prions are just proteins. They don't have any other macromolecules. Prions have capacity to form copies through replication. They replicate through free radical and chain mechanism. 

Doctor Stainly pruisne work on prions and show it's relation with disease called mad cow disease. ( This is neurodegenerative disease and responsible for harmful effects on brain).

In Australia sheep was infected with prions, caused scarpie disease in sheep. Organs of sloghed sheep were used in cow feedd. When cow consume feed, prions were transmitted to cow and cow start to show unusual behavior.

Symptoms of prions infection are like that of some disease 

1. Kurulyprosy
2. Insomnia
3. Dimensia

Detection of prions: Prions can be detected by Western bloting.

Normal prions:

Normal prions are present in our body. They don't have tendency to form rigid aggregate. They are quite less in number. They have following functions

1. Cellular differentiation
2. Store elemental surplus that is used in future
3. Memory enhancement

Molecular basis of prions:There is some difference in structure of Normal and abnormal prions.

1.  Normal prions have molecular weight 33-35KD while abnormal prions have molecular weight 27-30KD
2. In normal prions at position 178 amino acid aspartate is present while in abnormal prions at 178 position asparagine is present. 

Prions diagnosis and analysis:

1. Brain biopsy....in past for taking sample brain biopsy was used but now a days tonsils biopsy is used for sampling.

Immuno fluorescence:Biopsy sample is taken on slide and it is treated with antibody ( of abnormal prions) which is against normal prions. Speciality of antibody is that when it bind with abnormal prion it will glow. If we capture fluroscene it's mean abnormal prion is present in sample. As abnormal prion antibody was label with fluroscene probe. So patient sample will show fluroscene while normal sample will not show fluroscene.

Transmission of prions: Normally prions can't Cross specie barrier they transmitted through different ways. Like as formite

If a person is effected with prions and he has wound in head and his comb is used by another person so prions can be transferred to other individual. Comb is Carrier of prion.

Prions are very slow acting immune system can't destroy them.