module 4 set b Flashcards
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 light that comes out the other side
absorption spectroscopy
it is about measuring the absorbance or how much light does not come through the other side
absorption spectroscopy
the absorbance of a given sample depends on three things:
- intrinsic ability of the molecules in solution to absorb light
- the concentration of the molecules in solution
- path length of the light as it passes through the sample
a measure that accounts for both concentration and thickness of the sample being studied
molar extinction coefficient
graph of the absorbance versus the wavelength or frequency of light
absorption spectrum
can be used to identify types of molecules in a sample
absorption spectrum
can be also used to measure the concentration of molecules in solution
absorption spectroscopy
can be used to follow conformational transitions and ligand binding
absorption spectroscopy
measures absorbance across range of temperatures
temperature scanning absorption spectroscopy
useful for studying temperature-induced conformational transitions, that is, changes in molecular shape that can be brought about by changes in temperature
temperature scanning absorption spectroscopy
electrons drop down their excited state, emitting light in the process
fluorescence
true or false:
fluorescence is caused by absorption, although not all absorption results in fluorescence
true
can be used to characterize molecules and to measure and follow conformational transitions and ligand binding
fluorescence spectroscopy
a small molecule or the specific part of a molecule that is responsible for the fluorescence
fluorophore
a technique in which a fluorophore is attached to another process
fluorescent tagging
one of the techniques used to determine the sequence of residues in DNA
fluorescent tagging
technique uses a genetic tag that produces a stoichiometric ratio of a fluorescent protein reporter and the protein of interest during protein translation
protein quantitation ratioing
type of EM spectroscopy that differs from most forms of EM spectroscopy
nuclear magnetic resonance spectroscopy (NMR)
involves interaction of light with the nuclei of atoms in a molecule, whereas most forms of EM spectroscopy involve interaction of light with the electrons in the molecule
NMR
can provide much more structural details than other forms of spectroscopy
NMR
involves application of a strong magnetic field to the sample being studied
NMR
uses EM in the radio frequency portion of the spectrum
NMR
works on the basic principle that a spinning charge generates a magnetic field
NMR
frequency of what radiation will be proportional to the energy between two spin states
EM radiation
true or false
the nuclei that are less shielded by electrons and other atoms will be more exposed to the magnetic field
true
a 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
mass spectrometry
can also reveal information about the structure of molecules
mass spectrometry
a technique for determining the relative positions of atoms within a crystal
xray crystallography
an orderly, three-dimensional, repeating arrangement of atoms or molecules
crystal
this means that conditions can be arranged so the intermolecular forces cause the molecules to line up in an organized, repeating manner
many substances can be crystallized
provides very precise, high-resolution structural information for molecules in a crystal
xray crystallography
was used to discover that DNA is a double helix
xray crystallography
advantage of xray crystallography
it provides high resolution of structural detail
disadvantage of xray crystallography
the molecules must be in crystalline form in order for the technique to work
xray cyrstallography operates on the principle of what
diffraction
occurs when light waves pass through an ordered arrangement of openings and interfere with each other on the other side
diffraction
the peaks become higher and throughs become lower
constructive interference
the waves flatten out and lower the intensity of radiation
destructive interference
the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye
microscopy
the most powerful light microscopes provide only enough magnification to view objects larger than _________ nm
200 nm
physicist who experimented with the magnetics lenses for focusing electron beams and realized that it was possible to take advantage of smaller wavelength of electrons to create a imaging device theoretically capable of greater magnification than a light microscope
ernst ruska
who built the first electron microscope
ruska and knoll
2 most common types electron microscope
- transmission electron microscopy (tem)
- scanning electron microscopy (sem)
similar to light microscopy in that beam passes through a very thinly sliced sample to provide an image on the other side
transmission electron microscopy (TEM)
the image is made by focusing the electro beam onto a view screen coated with some material that fluoresces in response to the incoming electrons
transmission electron microscopy (TEM)
the electron beam is gradually scanned across the surface of the specimen
scanning electron microscopy (SEM)
provides more three dimensional image instead of a cross sectional slice of the specimen
scanning electron microscopy
provides magnified images similar to those of SEM but with resolution similar to those of TEM
atomic force microscopy (AFM)
works by moving a mechanical probe across the surface of the object being scanned
AFM
all are part of the more general class of techniques called
scanning probe microscopy (SPM)
an instrument that uses focuses laser beams to create piconewton (10^-12N) size forces that can be used to hold and manipulate microscopic particles, even as small as single molecule or atom.
optical tweezers
the phenomenon of focused laser beams holding a single particle in place in three dimensions is called an
optical traps
can be used tot hold and manipulate particles anywhere from 0.1nm to 10,000nm in size and have been used to trap single viruses, DNA molecules, bacteria, living cells, and organelles
optical tweezers
particularly useful for investigating the mechanics of and forces associated with molecular motors
optical traps
a technique used in electrophysiology to measure and characterize electric currents in cells, particularly in excitable tissue cells such as neurons
voltage clamp
the value of the voltage that is held constant is called
command voltage
how is voltage clamp technique held constant
through a feedback mechanism
what detects event the slightest change in the voltage and immediately pumps current across the membrane through the electrode to keep the voltage at the command voltage
feedback mechanism
allows us to measure the cell’s electric current under a variety of conditions
voltage clamp
a technique that the electrode feedback mechanism is used tot keep the current constant while allowing the voltage to vary
current clamp
an alternative technique for applying the electrode to the cell.
patch clamp
allows us to investigate the behavior of a single ion channel within the membrane
patch clamp
measurement of energy changes in form of heat
calorimetry
instrument designed to measure heat energy
calorimeter
can be used to determine the amount of energy necessary to unwind a piece of DNA helix
calorimetry
can be also used to measure the binding strength of various drugs to a particular protein
calorimetry
useful for measuring the very small amounts of energy associated with many biophysical processes
microcalorimeter
remember
Patch clamp measures the flow of ions through individual ion channels, voltage clamp maintains a constant membrane potential to record the resulting currents, and current clamp injects current to measure the resulting changes in membrane potential in a neuron.
glhf
