how to distinguish monomer and dimer without wetlab techniques

Question

[dineshtripathy9658]

how do you distinguish between a monomer and a dimer? i mean without wetlab techniques

[Pierre Lindenbaum]

the monomer is alone while the dimer is not.

[Bharat Iyengar]

Monomer of what?

[dineshtripathy9658]

protein...monomer of protein

Answer 1

[mth.vel]

Look for REMARK 350 of respective pdb coordinate file .

For example:

http://www.rcsb.org/pdb/files/3O26.pdb 
REMARK 350 BIOMOLECULE: 1                                                       
REMARK 350 AUTHOR DETERMINED BIOLOGICAL UNIT: MONOMERIC                         
REMARK 350 SOFTWARE DETERMINED QUATERNARY STRUCTURE: MONOMERIC                  
REMARK 350 SOFTWARE USED: PISA                                                  
REMARK 350 APPLY THE FOLLOWING TO CHAINS: A                                     
REMARK 350   BIOMT1   1  1.000000  0.000000  0.000000        0.00000            
REMARK 350   BIOMT2   1  0.000000  1.000000  0.000000        0.00000            
REMARK 350   BIOMT3   1  0.000000  0.000000  1.000000        0.00000 

http://www.rcsb.org/pdb/files/1R7A.pdb

REMARK 350                                                                      
REMARK 350 BIOMOLECULE: 1                                                       
REMARK 350 AUTHOR DETERMINED BIOLOGICAL UNIT: DIMERIC                           
REMARK 350 APPLY THE FOLLOWING TO CHAINS: A, B                                  
REMARK 350   BIOMT1   1  1.000000  0.000000  0.000000        0.00000            
REMARK 350   BIOMT2   1  0.000000  1.000000  0.000000        0.00000            
REMARK 350   BIOMT3   1  0.000000  0.000000  1.000000        0.00000            
REMARK 500