The chirality of chemical compounds is of undisputed importance in science and technology. In particular with respect to pharmacological application most molecules of interest cannot be accessed by the powerful techniques developed in recent years for gas phase analytes. Here, we demonstrate that the combination of electrospray ionization (ESI) with the detection of photoelectron circular dichroism (PECD) provides access to chirality information applicable to molecular materials with negligible vapor pressure, e.g. amino acids. To this end, glutamic acid and 3,4-dihydroxyphenylalanine (DOPA) have been electrosprayed into the source of a chirality spectrometer, where photodetachment is enforced and the PECD is detected. The technique can be expected to be conceptually applicable to all chemical systems with chirality based on molecular properties.
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Hello there!
I have implemented an air-chiral slab-air domain following the indications in this text:ComsolChiralSlab
I get a different reflectance curve in terms of the chirality term (Xi), and I recover the usual results for Xi=0. My main problem is I cannot visualize properly the differences between LCP and RCP. Basically what I have done is:
- Prepara a TE-mode physics problem (ewfd) (Ex=0 Ey=0 Ez=1).
- Prepare a TM-mode physics problem with an offset of pi/2 (ewfd2) (Hx=0 Hy=0 Hz=i).
- Prepare a TM-mode physics problem with an offset of -pi/2 (ewfd3) (Hx=0 Hy=0 Hz=-i).
- Run a Electromagnetic Wave Frequency Domain, Wavelength Study. (ewfd+ewfd2) Parametric alpha sweep.
- Run a Electromagnetic Wave Frequency Domain, Wavelength Study. (ewfd+ewfd3). Parametric alpha sweep.
- Then, in plot, I've written down:
- 0.5*abs(ewfd.S11)^2+0.5*abs(ewfd2.S11)^2 RCP reflectance
- 0.5*abs(ewfd.S11)^2+0.5*abs(ewfd3.S11)^2 LCP reflectance
Also I have tried to replace points 5 and 6 by one-study-two-steps, and I get different results. But I'm not sure about this last method.
What do you think?
UPDATED: I've also found this paper, but I don't understand very well the implementantion of the LCP and RCP in the way that's explained.
From the time of Luis Pasteur circular polarized light has found many applications in chemical analysis and spectroscopy. In their Communication (DOI: https://doi.org/10.1002/anie.20201114610.1002/anie.202011146), J. KapitΓ‘n, Y. Xu, P. BouΕ etβ al. report another modality, interference of Raman optical activity and circular dichroism, occurring during measurement of transition metal complexes. The chirality of the complex can be detected in Raman scattering of a solvent, the effect is strong and may find applications in detection of chiral compounds.
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Journal of the American Chemical SocietyDOI: 10.1021/jacs.9b11453
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Previously, we and other laboratories have reported an unusual and strong Raman optical activity (ROA) induced in solvents by chiral dyes. Various theories of the phenomenon appeared, but they were not capable of explaining fully the observed ROA band signs and intensities. In this work, an analysis based both on the light scattering theory and dedicated experiments provides a more complete understanding. For example, doubleβcell magnetic circular dichroism and magnetic ROA experiments with copperβporphyrin complexes show that the induced chirality is observed without any contact of the solvents with the complex. The results thus indicate that a combination of electronic circular dichroism (ECD) with the polarized Raman scattering is responsible for the effect. The degree of circularity of solvent vibrational bands is a principal molecular property participating in the event. The insight and the possibility to predict the chirality transfer promise future applications in spectroscopy, chemical analysis and polarized imaging.
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From what i understand CD follow Beer-Lamberts law , but have not found anything about if i can use this to find out the protein concentration and if it's even usefull to use this method.
I don't fully understand circular dichroism and how it works. I realize its circularly polarized light that interacts only with chiral molecules.What stumps me is how do the electronic and magnetic components of light interact with the sample and what are we measuring when we take a reading? do we measure both components of light?
I'm hoping to learn circular dichroism, but despite spending the afternoon reviewing the topic, I cannot find a physical explanation of CD spectra in terms of the molecular structure it describes, particularly regarding protein structure. I am aware that much of protein CD simply uses standard spectra for characteristic secondary structure in order to determine the proportions of different secondary structure elements within the protein, but I'm hoping to find an explanation of those standard spectra.
Specifically, I am interested in an explanation of why certain structure elements (alpha helices) absorb greater levels of left circularly polarized light than other structural elements(beta sheets) at one wavelength while that trend is reversed at higher wavelengths.
Here is a relevant link. See page 7 for the "standard spectra" that I am describing: http://www.chem.uci.edu/~dmitryf/manuals/Fundamentals/CD%20spectroscopy.pdf
Thanks! Ryan
Lets say you want to titrate a smll molecule ligand against a 20kDa protein and detect any conformational change that occurs. I know you could use CD or NMR to do this. NMR has obvious advantages of peak assignment, but what about comparing the sensitivity of the two. Is it possible that my ligand of interest could induce a conformational change in my 20kDa protein that is detectable by NMR, but not by CD (or vice versa).
This one is tricky as I can't find it on Pubmed or anything.
Title: Studies of cyanide binding to myeloperoxidase by electron paramagnetic resonance and magnetic circular dichroism spectroscopies.
Authors: Eglinton, D.G.; Barber, D.; Thomson, A.J.; Greenwood, C.; Segal, A.W.
Citation: Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular Enzymology vol. 703 issue 2 May 3, 1982. p. 187-195
A few links:
I've requested a copy on Researchgate but I have no idea how long that takes to go through. Could be days, weeks, months... Any help from you folks?
I am doing a paper/presentation on vibrational circular dichroism, and the one thing I am having trouble with is understanding how the different forms (right- and left-circularly polarized) interact differently with enantiomers.
My professor (who helped develop the technology with Lawrence Nafie) pointed me towards the Born-Oppenheimer Approximation, but I don't understand where that fits in.
Any pointers welcome.
By their conformational flexibility, MΓΆbius aromatic hexaphyrins provide a dynamic chirality attractive to develop stimuli responsive systems such as chiroptical switches. A regular [28]hexaphyrin has been equipped with a chiral coordinating arm to achieve transfer of chirality from a fix stereogenic element to the dynamic MΓΆbius one. The arm allows straightforward formation of labile monometallic Zn(II) complexes with an exogenous ligand, either a carboxylato or an amino with opposite inwards / outwards orientations relative to the MΓΆbius ring. As a corollary, the chiral coordinating arm is constrained over the ring or laterally, inducing opposite P and M MΓΆbius configurations with unprecedented high stereoselectivity (diast. excess greater than 95 %). By tuning the transfer of chirality, these achiral effectors generate electronic circular dichroism spectra with bisignate Cotton effect of opposite signs. Switching between distinct chiroptical states was ultimately achieved in mild conditions owing to ligand exchange, with high robustness (10 cycles).
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I don't want to step on anybody's toes here, but the amount of non-dad jokes here in this subreddit really annoys me. First of all, dad jokes CAN be NSFW, it clearly says so in the sub rules. Secondly, it doesn't automatically make it a dad joke if it's from a conversation between you and your child. Most importantly, the jokes that your CHILDREN tell YOU are not dad jokes. The point of a dad joke is that it's so cheesy only a dad who's trying to be funny would make such a joke. That's it. They are stupid plays on words, lame puns and so on. There has to be a clever pun or wordplay for it to be considered a dad joke.
Again, to all the fellow dads, I apologise if I'm sounding too harsh. But I just needed to get it off my chest.
Do your worst!
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c07140
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Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c00646
https://ift.tt/39K1Soq
