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Sensors > Ch 9: Fluorescence > Flashcards

Ch 9: Fluorescence Flashcards

1
Q

Why is a fluorescent dye superior to colorimetric dyes?

A

Fluorescent dyes can be excited at specific wavelengths, enabling selective detection and higher sensitivity​

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2
Q

What is photobleaching? How can it be minimized?

A

Photobleaching is the loss of fluorescence due to prolonged exposure to excitation light. It can be minimized by using lower light intensity, anti-fade reagents, or minimizing exposure time​ Loss of fluorescence due to light exposure; minimized with anti-fade agents and reduced light intensity.

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3
Q

Describe the fluorescence of NAD+ vs. NADH.

A

NAD+ does not fluoresce, whereas NADH emits fluorescence at ~460 nm upon excitation​

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4
Q

What is fluorescence?

A

The emission of light by a substance that has absorbed light or electromagnetic radiation, typically at a longer wavelength.

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5
Q

What are fluorophores?

A

Molecules that absorb light at a specific wavelength and re-emit it at a longer wavelength.

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6
Q

Define Stokes shift.

A

The difference between the excitation wavelength and the emission wavelength of a fluorophore.

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7
Q

What are common uses of fluorescence in biosensors?

A

DNA detection, protein analysis, and cellular imaging.

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8
Q

How is autofluorescence different from fluorescence?

A

Autofluorescence is the natural emission of light by biological substances without the addition of fluorophores.

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9
Q

Why is fluorescence more sensitive than colorimetric detection?

A

Fluorescence can be detected at lower concentrations due to its higher signal-to-noise ratio.

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10
Q

What is photobleaching?

A

The irreversible loss of fluorescence due to prolonged light exposure.

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11
Q

How can photobleaching be minimized?

A

Using anti-fade reagents, reducing light intensity, or limiting exposure time.

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12
Q

What are GFP and SYBR Green?

A

GFP (Green Fluorescent Protein) is a natural protein-based fluorophore; SYBR Green is a synthetic dye used for nucleic acid staining.

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13
Q

What is a DNA intercalating dye?

A

A dye that inserts itself between DNA base pairs and fluoresces upon binding.

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14
Q

How do optical filters enhance fluorescence detection?

A

They isolate specific wavelengths for excitation and emission, reducing background noise.

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15
Q

What is the role of NADH in fluorescence?

A

NADH fluoresces under UV light, useful in metabolic studies.

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16
Q

What is the difference between 180° and 90° fluorescence detection?

A

180° detects fluorescence in the same direction as excitation light, while 90° detects it orthogonally to minimize scattering.

17
Q

Why is fluorescence used in urine analysis?

A

Urine contains autofluorescent compounds that can indicate health conditions.

18
Q

How does chlorophyll exhibit fluorescence?

A

It absorbs light in the blue and red regions, emitting fluorescence in the red region.

19
Q

What are quantum dots?

A

Semiconductor nanocrystals that fluoresce with high brightness and stability, used in imaging and diagnostics.

20
Q

What is the principle of a fluorescence spectrometer?

A

It measures emitted light intensity across wavelengths after a sample is excited at a specific wavelength.

21
Q

Why is fluorophore stability important in biosensors?

A

Stability ensures consistent and reliable fluorescence signals over time.

22
Q

What is FRET (Förster Resonance Energy Transfer)?

A

A technique where energy transfer between two fluorophores is used to study molecular interactions.

23
Q

How are fluorescent dyes sorted by excitation/emission wavelength?

A

Based on their chemical structure, which determines the wavelengths they absorb and emit.

24
Q

Q: Why is a fluorescent dye superior to colorimetric dyes?

A

A: Fluorescent dyes allow selective excitation and higher sensitivity.

25
Q

Q: How do you sort fluorescent dyes by excitation/emission wavelength?

A

A: Examine their chemical structures to determine absorption/emission properties.

26
Q

Q: What is a DNA intercalating dye?

A

A: A dye that inserts between DNA bases and fluoresces upon binding.

27
Q

Q: What is photobleaching? How can it be minimized?

A

A: Loss of fluorescence due to light exposure; minimized with anti-fade agents and reduced light intensity.

28
Q

Q: How does NAD+ fluorescence differ from NADH?

A

A: NADH fluoresces, while NAD+ does not.

29
Q

Q: Which urine component causes autofluorescence?

A

A: Urobilinogen; excitation: blue, emission: green.

30
Q

Q: What colors does chlorophyll absorb and emit?

A

A: Absorbs red/blue, emits red fluorescence.

31
Q

Q: How can fluorescence emission be isolated?

A

A: Using optical filters, angled detection, or optical fibers.

32
Q

Q: How does fluorescein intensity differ above/below the air-water interface?

A

A: Reflectance varies due to refractive index changes.

Sensors (14 decks)

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