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Questions related from Sumanth Kumar
I am trying to fix the nucleosomes by formaldehyde. The idea is to make the nucleosomes stable at high salt concentration and temperature by crosslinking DNA with Histone octamer. We have...
02 February 2019 7,262 4 View
I am trying to measure stiffness of red blood cells in RPMI using AFM force spectroscopy method. In literature, the typical indentation of RBC at a force of 500pN is 500nm. But in my case I see...
07 July 2018 8,992 6 View
I am imaging nucleosomes using AFM. I purchased nuclesomes from EpiCypher. The storage buffer contains 10mM TrisCl, 1mM EDTA, 25mM NaCl, 2mM DTT, pH 7.5. I have the stock solution (2ug/ul) kept at...
07 July 2018 7,309 3 View
We use APTES for silanization of glass surface. We observed that 4% APTES prepared in acetone turns yellow within 24hours. But the new batch of APTES (Sigma) in acetone is not turning yellow with...
06 June 2018 1,453 3 View
I am performing AFM force spectroscopy on red blood cells by immobilizing them on glass surface. I clean the glass coverslips by sonication in soap solution, Milli Q, ethanol, acetone, ethanol for...
03 March 2018 1,274 3 View
I am using tapping mode AFM in MilliQ to image a plasmid PGEM3Z which is ~1um long circular DNA. I prepare the sample in the following way. I take 15mm x 15mm mica sheet and cleave it using scotch...
01 January 2018 1,737 4 View
I would like to prepared a DNA sample that has -SH or thiol group at one of its end so that I can covalently immobilize it on a surface. The -SH modified primers are commercially available. I am...
12 December 2017 7,318 8 View
I would like to attach DNA to AFM tip and image it using SEM to check if coating was done properly. I couldn't find any papers that show SEM images of DNA. I would like to know the protocol to do...
11 November 2017 6,687 3 View
I have purchased human histone octamers from Sigma (SRP0408) for nucleosome reconstitution experiments. I would like to check the protein complex in octameric form. Running it on SDS-PAGE will...
10 October 2017 7,392 7 View
I am measuring a sample of histone octamer which is in buffer containing 20mM Tris-HCl, 1mM EDTA, 2M KCl, 10mM DTT, 0.5mM Benzamidine and MilliQ water. I have prepared 1M Benzamidine in Ethanol...
09 September 2017 5,997 8 View
I need to covalently attach DNA to glass surface. There are procedures to attach DNA if it is amine or thiol terminated. I saw papers where they synthesize them. But are they commercially...
07 July 2017 7,340 3 View
I would like to prepare mono nucleosomes for my single molecule experiments. We have PGEM 3Z vector (size is 3kb) from which we are amplifying the 344bp oligo that contains the Widom 601 sequence...
07 July 2017 7,335 1 View
I am trying to perform APTES coating on glass coverslips and AFM tips. I need the most anhydrous organic solvent to dissolve APTES so that there wont be any polymerization of APTES. I have seen...
07 July 2017 2,677 3 View
I am trying to perform covalent immobilization of streptavidin protein on glass surface. This is done by first coating the glass with 2% APTES-toluene and then with 2.5% glutaraldehyde-water...
07 July 2017 6,993 9 View
I am trying to measure the affinity of biotin to bind to streptavidin using AFM force spectroscopy. I would like to know the what buffer should be used and the pH to be maintained in which the...
06 June 2017 7,589 3 View
I would like to coat AFM tip with APTES and found that 10% APTES is the solution in which tips are placed and incubated for 2hrs. I have seen papers mentioning the usage of solvents like acetone,...
06 June 2017 6,571 14 View
At some points in space the director of the molecules in nematic crystals is undefined which are called defects. Disclination line is one of the types. I find it difficult to understand what it...
12 December 2014 6,812 1 View
I have read that monochromatic light is always polarized as they say that there is always a constant phase difference between the x and y components of the electric field. And that the unpolarized...
11 November 2014 5,012 5 View
Please give a physical description about it and examples where we encounter it in studying astrophysics.
10 October 2014 8,916 2 View
In a birefringent crystal, the incident light gets split into two beams. One is ordinary and the other is extraordinary rays. The ordinary ray experiences constant refractive index n_o but the...
10 October 2014 5,306 9 View
I have seen that both classical and quantum theories are developed for this phenomenon. So please explain me the need for this.
10 October 2014 6,893 4 View
In experiments we only deal with hermitian operators and they are called physical observables. But in quantum theory non-hermitian operators also exist. Are we using them only as a mathematical...
10 October 2014 9,714 14 View
I consider a Mach-Zehnder interferometer. It is said that this setup cannot be phase stabilized properly because it has light travelling in two arms, whereas it is more stable in the case of...
10 October 2014 4,601 5 View
Consider three mutually commuting observables from Mermin's square, A_1=σ_x⊗I, A_2=I⊗σ_x, A_3=σ_x⊗σ_x, where σ_x is the Pauli operator and I is the identity operator. We can see that...
09 September 2014 1,661 4 View
As we know, annihilation operator is a non-hermitian operator which can take complex eigenvalues. I would like to know if the eigenvalue of this operator was ever observed in the laboratory or at...
08 August 2014 1,103 4 View
