Unanswered Questions

14
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0answers
332 views

Is there a general consensus on the causes of the $\alpha$-effect?

There have been various explanations posited for the $\alpha$-effect. It is currently in the list of unsolved problems in chemistry on Wikipedia, but, due to a lack of references to that effect, I'm ...
8
votes
0answers
106 views

Hyperlithiated Carbon Species

Below is replicated Question 1 from the Final Qualifying Exam of the Australian Chemistry Olympiad, 2004B, here. Question: The theory of promotion-hybridization is quite successful at explaining why ...
8
votes
0answers
552 views

Stoichiometric defects in ionic crystal?

The stoichiometric defects (Schottky and Frenkel defects) in ionic crystals are formed due to irregularities in ionic arrangement all the while maintaining the stoichiometry and electric neutrality. ...
8
votes
0answers
240 views

What is Cβ (C-beta) deviation?

Molprobity and some other protein structure validation tools report a Cβ deviation statistic and offer plots for it (example below). Apparently if the Cβ is greater than 0.25 Å, some ...
7
votes
0answers
40 views

Is greater relative AA battery capacity at high currents indicative of greater capacity at low currents?

I originally posted this on EE.SE but might be better here: Battery showdown compared the mAh and mWh capacity of different AA batteries discharged at 200mA. Would the relative capacities of each ...
7
votes
0answers
99 views

Why does depurination happen at a higher pH (or under less harsh conditions) than depyrimidation?

I've always wondered why the N-glycosidic bond, which connects the adenine or guanine purine bases to their sugars, was the easiest to cleave via acid hydrolysis, or why purines have the lowest ...
7
votes
1answer
105 views

Is there any relationship between ultrasonication and temperature

In chemistry we use ultrasonication for cleaning vessels ,synthesis of chemical compounds (sonochemistry) etc.I know that during ultrasonication high temperature and pressure is formed "locally".But I ...
7
votes
0answers
63 views

When measuring avidity should you use the ligand concentration or the nanoparticle concentration?

Looking at avidity between a ligand-receptor, you're looking at an enhancement of the $K_d$ compared to a lone ligand. Is it more appropriate to compare the $K_d$ using the concentration of the ...
7
votes
0answers
96 views

How can I update a map/mesh and coordinates in a PyMol session file?

I have a PyMol session file I was using to create my figures. It contains a protein and ligand broken into several groups of atoms with a fair bit of overlap. There are also a few meshes built from ...
5
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0answers
53 views
+50

When is it true that more nodes equals higher energy?

Consider all the MOs of some isolated molecule. (It could be a single atom too; I'll use MO to refer to AOs as well.) Number them in increasing order of the number of nodes (node = surface where the ...
5
votes
0answers
58 views

What is the origin of the differences between the MO schemes of O2 and N2?

Here are the MO schemes of $\ce{N2}$ (left) and $\ce{O2}$ (right). Why is the $\sigma$-MO formed by the $p$ AOs energetically above the $\pi$-MO for $\ce{N2}$ but not for $\ce{O2}$? Can it be ...
5
votes
0answers
56 views

Why does increasing number of salt bridges increase voltage of electrochemical battery?

In an experiment, I set up a cell with lead nitrate (w/ lead electrode) and zinc sulfate (w/ zinc electrode), with a salt bridge containing potassium nitrate. I observed that by increasing the number ...
5
votes
0answers
42 views

How does the crystal know where to stop stacking the unit cells?

I tried to make different crystals in the cubic system by stacking cubes in a 3d software. However I need to tell the software where to skip rows or stop stacking the unit cells in a specific ...
5
votes
0answers
104 views

Natural Bond Orbital (NBO) analyses: Physical significance/interpretation of E(2) 'stabilization energy'?

PREFACE: I am no expert on this topic. My questions at the bottom may be off base. I have some experience with symmetry-adapted perturbation theory (SAPT) when it comes to analyzing intermolecular ...
5
votes
0answers
189 views

Is there an energy cost associated with flipping the spin of an electron?

THE STORY: A common example used to illustrate the limitations of restricted Hartree-Fock (RHF) theory is the H$_2$ dissociation energy ($D_e$) curves. RHF enforces electrons to be paired into spin ...

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