The Folding And Unfolding Dynamics Of Proteins In Low Concentration GdmCl Studied By Magnetic Tweezers

Single molecule manipulation technology becomes more and more popular recently,It is a useful tool to study the biological macromolecules.Magnetic tweezers,as a single-molecule manipulation technique,can easily measure individual bio-macromolecules.It is also capable of stable and long time measurement.GB1 is a protein on the surface of a streptococcal cell Immunoglobulin binding domain.It can help the host escape the host's immune system.Although it does not have the relevant mechanical function in the body,it has a very good mechanical stability.GB1 proteins also show a unique combination of mechanical features,including the fast folding and unfolding kinetics and high folding fidelity.Traditional biochemical experiments can only be carried out in the guanidine hydrochloride(GdmCl)solution above 3M of concentration of GB1 protein,because in the low concentration of GdmCl,the protein can not unfold spontaneously.But single molecule manipulation technology can apply an external force on the samples to unfold the proteins.This makes it possible to study the unfolding of proteins in low concentrations of GdmCl.This paper hopes to further understand the mechanism of protein folding and folding by the study of folding and folding of the GB1 protein in GdmCl solution.We used a magnetic tweezers technique for a long time and stable measurements.The GB1 protein was folded and unfolded in different kind of solutions,such as OM,100mM,500mM GdmCl.Experiments were carried out in the above solution environment with a tensile force of 4 to 100 pN.This is the first time to use magnetic tweezers on the GB1 protein study for such a long time.In the process,we have not only measured the folding and unfolding rate under different conditions,but also do some simple analysis of folding and unfolding dynamic.In the equilibrium measurement of 500mM GdmCl under the force of 8 pN,we discovered a misfolded state of GB1.This discovery is important to understand the protein folding and folding mechanism.The study of protein misfolding is very important to understand the mechanism of some diseases caused by misfolded proteins,such as Creutzfeldt-Jakob disease.