Quiz 2 Flashcards

Question

Advantages of two-photon excitation

Answer 1

Less phototoxicity Improved spacial resolution Larger depth (less mie scatter)

Answer 2

material that can be polarized in an external electric field, but charges do not flow through it

Answer 3

is due to loss of high- frequency spatial information in optical microscopy resulting from the diffraction of light when it propagates through a distance larger then the wavelength of light (far field)

Answer 4

3D distribution of the image of a point object

Answer 5

Michelson Fabry-perot Sagnac Mach Zenhder

Answer 6

Traditional superresolution method Distance between aperture and sample is smaller than wavelength of light

Answer 7

Cantilever is used on metal. beam which enhances sample signal

Answer 8

● In regular printers, droplets cannot be deposited in small amounts on paper due to surface tension ● High-resolution printing can be achieved by packing the nozzles very densely ● Printing of organic materials, including DNA, is possible

Answer 9

Cantilever tip is scanned over sample surface ● Laser reflects off of the cantilever tip; this allows for sub-nm resolution to be achieved ● Provides information about local stiffness and topography of a sample

Answer 10

the field that searches for certain markers within a biological medium.

Answer 11

Protein: ELISA, Gel electrophoresis, Microarray Nucleic acids: PCR, gel electrophoresis, Microarrays, fish Cell: microarrays, flow cytometry, microscopy

Answer 12

1. The capture antibody is fixed to the wells of well plate 2. The sample containing the antigen is placed in the well 3. Primary antibodies are added to the wells, to form a complex with the target the antigen 4. Secondary antibodies are labelled with enzyme; bind to the primary antibody 5. A substrate is added to the well; this will react with the enzyme to produce a colour in the solution. 6. The intensity of the colour measured in a well is then proportional to the amount of antigen present in that well.

Answer 13

Direct: ● The primary conjugate antibody is labelled with the enzyme, this antibody binds to the fixed antigen, and reacts with the substrate to produce colour Indirect: ● A primary antibody binds to the antigen ● The secondary conjugate antibody is labelled with the enzyme ● Used to amplify the signal - the primary antibody has multiple binding sites, for multiple labelled secondary antibodies to bind

Answer 14

● Process that amplifies nucleic acid sequences through thermal cycling. ● It leads to the exponential growth of chains assuming a sufficient number of polymerase enzymes. ● Variants of this technique exist such as qPCR (quantitative PCR), isothermal qPCR, and rtPCR (reverse transcriptase PCR).

Answer 15

Involves the separation of nucleic acid fragments by molecular weight in a gel by generating an electric field that acts on the innate negative charge of nucleic acids. ● Shorter molecules move faster and migrate further through the pores of the gel ● By staining the gel after the experiment, bands allow for the identification of the fragment sizes. ● This is particularly useful in forensic analysis, as well as in sequencing.

Answer 16

● FISH is a technique that allows for specific DNA sequences to be identified on particular chromosomes. ● This can be used to track a target DNA strand in space and time throughout an experiment, and to quantify specific gene expression. ● It can be particularly useful for identifying pathogenic DNA sequences within a sample

Answer 17

1. Permeabilization: cells are treated with a mild surfactant to dissolve the cell membrane. The dye molecules can therefore be introduced into the cell. Note that electroporation is a valid alternative to this step. 2. Fixation: cell morphology is “frozen” in place. A chemical fixative is used to solidify bonds in proteins, increasing overall cell rigidity. 3. Mounting: cells are placed on a microscope slide. 4. Staining: cells are bathed in dyes and then rinsed. The cells can then be imaged under a microscope.

Answer 18

Light from the laser is reflected off the metallic plate and into a detector. ● At a certain angle (i.e., SPR angle), light is absorbed by the plate’s electrons, making them resonate. These electrons are called surface plasmons. ● Since a component of the light’s energy is absorbed by the electrons, the intensity drops, leading to a darker band on the detector. ● When a binding event occurs, the refractive index changes, and the dark band shifts ● This allows for the binding event to be identified. Analyte detection occurs due to this change in reflectivity.

Answer 19

Linearity: the accuracy of measured responses fall on a straight line. For a high substrate concentration, linearity should be quite high. Sensitivity: the minimum concentration of analyte that can be detected. The probability of a positive test result given that the condition is truly positive (the true positive rate, or TPR). It measures how a signal changes in response to a varying analyte concentration. Specificity: ability to distinguish the analyte from other components in the sample. The probability of a negative test result given that the condition is truly negative (the true negative rate, or TNR). Response time: the time necessary for the biosensor to achieve 95% of the total response.

Answer 20

Converts light to electrical signal (transducer) Reverse current in photodiode when light passes, proportional to incident light, sensitivity prop to the wavelength

Answer 21

Electrical (dielectric voltage or current), mech (cantilevers, mass, piezo), temp, electrochem (potential/current), optical (reflection, absorption, scattering, interference)

Answer 22

detects the presence of a ligand protein in a liquid sample using an antibody directed against the target protein

Answer 23

Analytic device that analyses an analyte using a biorecognition element.

Answer 24

medicine, research, plant pathogens, environmental monitoring, security, food safety, process industries