Quantum chemistry / Molecular quantum mechanics

[Nagelfar]

Just to have a blanket thread on the subject (because anything spilling over to the subject of the quantum laws as they're understood intrigues me with regard to molecular dynamics): does anybody know of any papers or research or specific phenomena / theories about the effects pertaining to the quantum scientific realm? As in, how it relates to neurologically/psychologically efficacious drugs / neurotransmitters (exogenous or endogenous, ligand relationships) i.e. molecular compounds and strange consequences that quantum mechanics bode on the playing field of QSAR / activity specifically?

Anything whatsoever that may be on this subject.

I'd like some insight as to where these worlds are seen to meaningfully overlap in the current academic establishments findings / discoveries. A very generic umbrella question, but hopeful that my request may garner some interesting discussion / debate and I may glean some new insights of any kind on the topic (since molecular drug workings as it can be construed in quantum terms is an area in which I have essential zero knowledge as of this posting)

 

[aced126]

I think quantum mechanics would mostly have a use in molecular binding studies. I think it can be used to determine the energy minimised conformation of a molecule; a conformation the molecule is likely to be in while bound. There are computers which can achieve all this I believe, but a firm understanding about how stuff like that is calculated would be very beneficial I'm guessing. I don't know a lot about quantum physics (only the very basics) but I hope to expand this knowledge one day.

 

[belligerent drunk]

Quantum chemistry is used a lot in molecular modeling of drugs and how they behave in certain solutions and around receptors. Quantum chemistry is the basis for programs which predict the most stable conformers and so on, and it is also used in modeling reactions and interactions. Personally, I don't believe that thorough fundamental understanding of quantum physics is a necessity per se - I lack one myself. It does help, but in this field a lot more important is a general understanding of how electron clouds and their densities behave and affect chemical processes, because after all bodily processes are mostly chemistry not deep physics.

Papers? I think if you look around then quite a lot of papers use some kind of computer input (which relies on quantum chemistry) as a start or reference point.

If you wish to educate yourself in the fundamental field of quantum chemistry, then I guess you have to take a course of theoretical chemistry, but I have to say that most likely you won't really need that knowledge. The most meaningful knowledge (as far as my experience goes) came from studying organic chemistry and reaction mechanisms. A thorough understanding of the latter most likely will form a universal understanding about how chemical matter behaves. The most important points are, I guess, electronegativity of elements (and that of them in compounds! Carbon's electronegativity rises quite a lot, even higher than 3.5, in certain configurations), soft/hard acid-base theory, the theory surrounding nucleo/electrophiles, secondary interactions (van der Waals + hydrogen bond)

What kind of debate are you intending to start by the way?

I'm sorry if my response missed the question, I'm not in the best headspace right now.

 

[polymath]

In principle one could predict the receptor affinities of any compound by using quantum mechanics, but in practice the calculation would be so computationally demanding that it would not be possible with current technology. Exact (as opposed to approximate) solutions for quantum mechanical problems are possible for only very simple systems like a hydrogen atom (a two-particle system composed of a proton and an electron). For a helium atom (three particle system) one already has to look for increasingly accurate approximations. The problem of receptor binding is a problem with thousands of particles.

I'm a PhD student in physics and I've also studied advanced quantum chemistry in university, so I reasonably well know what I'm talking about.

 

[belligerent drunk]

In principle one could predict the receptor affinities of any compound by using quantum mechanics, but in practice the calculation would be so computationally demanding that it would not be possible with current technology. Exact (as opposed to approximate) solutions for quantum mechanical problems are possible for only very simple systems like a hydrogen atom (a two-particle system composed of a proton and an electron). For a helium atom (three particle system) one already has to look for increasingly accurate approximations. The problem of receptor binding is a problem with thousands of particles.

I'm a PhD student in physics and I've also studied advanced quantum chemistry in university, so I reasonably well know what I'm talking about.

It is true that currently computational predictions are suggestive at best, we still need empirical data to have some kind of idea of the action of a drug. I'm doubtful though that data from purely theoretical calculations will be enough at any point in humans' life. There will still be the question/problem that maybe the calculations aren't right, so we'd need to test it practically. And in this scenario, where the calculations are only suggestive and secondary, they can be inaccurate to some degree. Of course, it's always good to know something for almost-sure, but even having an idea of a direction in which to go can be sufficient.

 

[atara]

First read Calculus Made Easy (Google it), then read through Brown and Churchill's Complex Variables and Applications until you learn the residue theorem and prove the convergence radius of a Laurent series (don't worry about the conformal mapping -- it shows up in physics but you won't need it for a long time), then read Hayward's Quantum Mechanics for Chemists or an equivalent text of your choosing, and from there search (Google Scholar or something) for some review articles in the particular domain of your choosing, in your case some kinda peptide chemistry and teach yourself the basics.

If you devote ten hours a week it should take you about a year or two. Might help to sign up for some classes.

 

[polymath]

Here's the book I studied quantum chemistry from... Someone has uploaded it on the net. http://www.kinetics.nsc.ru/chichinin/books/spectroscopy/Atkins05.pdf

 

[aced126]

First read Calculus Made Easy (Google it), then read through Brown and Churchill's Complex Variables and Applications until you learn the residue theorem and prove the convergence radius of a Laurent series (don't worry about the conformal mapping -- it shows up in physics but you won't need it for a long time), then read Hayward's Quantum Mechanics for Chemists or an equivalent text of your choosing, and from there search (Google Scholar or something) for some review articles in the particular domain of your choosing, in your case some kinda peptide chemistry and teach yourself the basics.

If you devote ten hours a week it should take you about a year or two. Might help to sign up for some classes.

I read the first few pages of Complex Variables and Applications, and I must say, they did a pretty poor job at introducing complex numbers lol. If I was new to complex numbers I would have been completely put off by the illogical "definition" of the product of 2 complex numbers; I know it is correct formally but they could have explained it logically; they do go on to eventually but that introduction is way too unintuitive; it's like when you get introduced to matrices and you always think how unintuitive the definitions are.

 

[atara]

^A textbook in complex analysis isn't meant to be your first introduction to complex numbers. Brown and Churchill use the formal definition first because they expect their readers to be familiar with the ordinary manipulation of complex numbers, as is often taught in pre-calculus or undergrad algebra.