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Linear dichroism

Linear dicrosim (LD) is also a very closely related technique to CD in which the difference between absorbance of perpendicularly and parallelly polarized light is measured. In this technique the plane of polaliration of light does not rotate. LD is used to determine the orientation of absorbing parts in space.

Advantages and limitations of cd

Just like any other instrument CD has its strengths and limits. The comparison between CD and NMR shown in [link] gives a good sense of capabilities of CD.

A comparison of CD spectroscopy to NMR spectroscopy.
CD NMR
Molecules of any size can be studied There is size limitation
The experiments are quick to perform; single wavelength measurements require milliseconds. This is not the case all of the time.
Unique sensitivity to asymmetry in sample’s structure. Special conditions are required to differentiate between enantiomers.
Can work with very small concentrations, by lengthening the cuvette width until discernable absorption is achieved. There is a limit to sensitivity of instrument.
Timescale is much shorter (UV) thus allowing to study dynamic systems and kinetics. Timescale is long, use of radio waves gives average of all dynamic systems.
Only qualitative analysis of data is possible. Quantitative data analysis can be performed to estimate chemical composition.
Does not provide atomic level structure analysis Very powerful for atomic level analysis, providing essential information about chemical bonds in system.
The observed spectrum is not enough for claiming one and only possible structure The NMR spectrum is key information for assigning a unique structure.

What kind of data is obtained from cd?

One effective way to demonstrate capabilities of CD spectroscopy is to cover the protein secondary structure study case, since CD spectroscopy is well-established technique for elucidation of secondary structure of proteins as well as any other macromolecules. By using CD one can estimate the degree of conformational order (what percent of the sample proteins is in α-helix and/or β-sheet conformation), see [link] .

CD spectra of samples with representative conformaitons. Adapted by permission from N. Greenfield, Nat. Proto. , 2006, 1 , 6.

Key points for visual estimation of secondary structure by looking at a CD spectrum:

  • α-helical proteins have negative bands at 222 nm and 208 nm and a positive band at 193 nm.
  • β-helices have negative bands at 218 nm and positive bands at 195 nm.
  • Proteins lacking any ordered secondary structure will not have any peaks above 210 nm.

Since the CD spectra of proteins uniquely represent their conformation, CD can be used to monitor structural changes (due to complex formation, folding/unfolding, denaturation because of rise in temperature, denaturants, change in amino acid sequence/mutation, etc. ) in dynamic systems and to study kinetics of protein. In other words CD can be used to perform stability investigations and interaction modeling.

Cd instrument

[link] shows a typical CD instrument.

A CD instrument.

Protocol for collecting a cd spectrum

Described is a general procedure for data collection, options (time constant of instrument, wavelength interval, half-bandwidth) can be varied according to needs through the instrument controlling program.

Questions & Answers

what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
advantages of NAA
Sai Reply
how I can reaction of mercury?
Sham Reply

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Source:  OpenStax, Physical methods in chemistry and nano science. OpenStax CNX. May 05, 2015 Download for free at http://legacy.cnx.org/content/col10699/1.21
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