Module 4 - SET B Flashcards
It is one of the more common and easy to understand forms of spectroscopy.
Absorption Spectroscopy
the light of a specific wavelength is incident through a sample and measure the intensity of the light that comes out the other side
Absorption spectroscopy
it is about measuring the absorbance, or how much light does not come through to the other side (i.e., how much light is absorbed)
Absorption spectroscopy
light is converted into the kinetic energy of electrons in an atom or molecule; this bumps the electrons into a higher or excited energy state.
absorption
Where does the absorbance of a given sample depends?
- The intrinsic ability of the molecules in solution to absorb light
- The concentration of the molecules in solution.
- The path length of the light as it passes through the sample.
True or False: If the sample container is larger, then the light has to pass through more of the solution before getting to the other side, and so more light will be absorbed
True
measure that accounts for both concentration and thickness of the sample being studied
molar extinction coefficient
express the absorbance in units that are per concentration and per length
molar extinction coefficient
graph of the absorbance versus the wavelength or frequency of light
absorption spectrum
True or False: Many molecules have unique characteristic absorption spectra, so an absorption spectrum can be used to identify types of molecules in a sample.
True
True or False: Many molecules have unique characteristic absorption spectra, however, an absorption spectrum cannot be used to identify types of molecules in a sample.
False
used to measure the concentration of molecules in solution (once the identity of the molecule is known)
Absorption spectroscopy
True or False: We can use the absorption spectroscopy to measure concentration of molecules in solution even if the molecule is unknown
False, the molecule must be known in order to know its concentration in a particular solution
True or False: Absorption of light does not vary with conformation and presence/absence of bound ligands.
False, it varies with conformation and presence/absence of ligands
can be used to follow conformational transition and ligand binding
absorption spectroscopy
measures absorbance (usually at single wavelength) across a range of temperatures)
Temperature scanning absorption spectroscopy
useful for studying temperature-induced conformational transitions, that is, changes in molecular shape that can be brought by changes in temperature
Temperature scanning absorption spectroscopy
common technique for studying conformational transitions in membranes, proteins, and DNA (nucleic acids)
Temperature scanning absorption spectroscopy
electrons drop down from their excited state, emitting light in the process
fluorescence
True or False: Fluorescence is caused by absorption, but not all absorption causes fluorescenece
True
Which is longer? The wavelength of the emitted light or absorbed light?
emitted light
can be used to characterize molecules and to measure and follow conformational transitions and ligand binding
Fluorescence spectroscopy and Absorption spectroscopy
small molecule or the specific part or a molecule that is responsible for the fluorescence
fluorophore
technique in which a fluorophore is attached to another molecule in order to track that molecule through some biological process
fluorescent tagging
one of the techniques used to determine the sequence of residues in DNA
fluorescent tagging
protein quantitation ratioing (PQR) technique uses a genetic tag that produces a stoichiometric ratio of a fluorescent protein reporter and the protein of interest during protein translation
Quantitation of protein levels in single cells in vivo
type of EM spectroscopy that differs from most forms of EM spectroscopy
Nuclear magnetic resonance spectroscopy
how does NMR differ in most forms of EM spectroscopy?
- NMR involves interaction of light with nuclei of atoms, whereas most forms of EM spectroscopy involve interaction of light with electrons in the molecule.
- Although most forms of spectroscopy provide some structural information, NMR can provide much more structural details (higher resolution) than other forms of spectroscopy.
- NMR involves the application of a strong magnetic field to the sample being studied. This magnetic field alters and limits some of the energy states available to the nuclei; this is what makes it possible to measure the absorption and emission of EM by the nuclei in the sample.
- NMR uses EM in Radio Frequency portion of the spectrum and fluorescent spectroscopy typically rely on ultraviolet, visible, infrared.
SHORT VER:
1. NMR interaction of light with nuclei of atoms in molecule while other interaction of light with electrons of molecule.
2. provide higher resolution
3. involves strong magnetic field that makes measuring absorption and emission possible
4. NMR uses Radio Freq while Fluorescent Scpetroscopy uses UV, visible, and infrared.
works on the basic principle that a spinning charge (such as the nucleus of an atom) generates a magnetic field
Nuclear Magnetic Resonance Spectroscopy
is like a small magnet
nucleus
True or False: under normal conditions, spins of nuclei are randomly oriented in any direction while in strong magnetic field, it is constrained to only certain orientations with respect to external magnetic field
True
typically parallel and antiparallel to the magnetic field
external magnetic field
True or false: when a nucleus jumps from one spin orientation to another, it will absorb or emit EM radiation
True
true or false: the frequency of the EM radiation emitted or absorbed during the change in spin orientation is inversely proportional to energy difference between the two spin states.
False, it must be proportional
True or False: The bigger energy difference between spin states means that nuclei will resonate with lower frequencies or less energy
False: The smaller energy difference
True or False: nuclei that are less shielded by electrons and other atoms will be more exposed to magnetic field and will resonate to higher frequency
true
technique in which molecules or parts of molecules are ionized and then passed through a magnetic field
Mass spectrometry
used both for determining molecular weights and for identifying molecules (once the molecular weight is known
Mass spectrometry
can be difficult to ionize in a quantifiable way and can be difficult to fly through a vacuum (a requirement for mass spectrometry)
large molecules
