2015年《生物信息获取技术》期末考试样题I．questions
1.The definition for microfluidic chip
A:Microfluidics is a multidisciplinary field intercting engineering, physics, chemistry, biochemistry, nanotechnology, and biotechnology, with practical applications to the design of systems in which low volumes of fluids are procesd to achieve multiplexing, automation, and high-throughput screening. Microfluidics emerged in the beginning of the 1980s and is ud in the development of inkjet print heads, DNA chips,lab-on-a-chip technology, micro-propulsion, and micro-thermal technologies.
Microfluidic chip is a device that integrates one or veral laboratory functions on a single chip of only millimeters to a few square centimeters to achieve automation and high-throughput screening, dealing with the handling of extremely small fluid volumes down to less than pico liters.
2.The difference between laminar flow and turbulent flow
A: Where air is flowing in a laminar manner it has less resistance than when it is flowing in a turbulent manner. If flow becomes turbulent, and the pressure difference is incread to maintain flow, this respon itlf increas resistance. This means that a large increa in pressure difference is required to maintain flow if it becomes turbulent.
Whether flow is laminar or turbulent is complicated, however generally flow within a pipe will be laminar as long as the Reynolds number is less than 2300.
This shows that larger airways are more prone to turbulent flow than smaller airways. In cas of upper airway obstruction the development of turbulent flow is a very important mechanism of incread airway resistance, this can be treated by administering Heliox which is much less den than air and conquently more conductive to laminar flow.
3.What is the rapid prototyping method for fabricating PDMS microchips?可爱小女孩头像
A: Rapid prototyping method is bad on photolithography, of which the whole schemes is as follows: a. fabricate master by rapid prototyping; b. place posts to define rervoirs; c. cast prepolymer and cure; d. remove replica from master; e. oxidize PDMS replica and flat in plasma and al
4.What are the advantages of PDMS for microchip fabrication?
A: a. It is transparent at optical frequencies (240 nM – 1100 nM), which facilitates the obrvation of contents in micro-channels visually or through a microscope.
b. It has a low autofluorescence
c. It is considered as bio-compatible(with some restrictions). The PDMS bonds tightly to glass or another PDMS layer with asimple plasma treatment.
d. PDMS, during cross-linking, can be coated with a controlled thickness on a substrate using a simple spincoat.
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e. It is deformable, which allows the integration of microfluidic valves using the deformation of PDMS micro-channels, the easy connection of leak-proof fluidic connections and its u to detect very low forces like biomechanics interactions from cells.pe装机
f. It is inexpensive compared to previously ud materials (e.婴儿体重计算
g. silicon).
g. The PDMS is also easy to mold, becau, even when mixed with the cross-linking agent, it remains liquid at room temperature for many hours.
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h. It is gas permeable. It enables cell culture by controlling the amount of gas through PDMS or dead-end channels filling (residual air bubbles under liquid pressure may escape through PDMS to balance atmospheric pressure).吃黑巧克力的好处
II. Essay
1. Discuss a bioinformation obtaining technology that you are interested in.
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A: Electrospray ionization(ESI) is a technique ud in mass spectrometry to produce ions using an electrospray in which a high voltage is applied to a liquid to create an aerosol. It is especially uful in producing ions from macromolecules becau it overcomes the propensity of the molecules to fragment when ionized. ESI is different from other atmospheric pressure ionization process (e.g.MALDI) since it may produce multiply charged ions, effectively extending the mass range of the analyr to accommodate the kDa-MDa orders of magnitude obrved in proteins and their associated polypeptide fragments.
Advantages and disadvantages: ESI is a so-called 'soft ionization' technique, since there is very little fragmentation. This can be advantageous in the n that the molecular ion (or more accurately a pudo molecular ion) is always obrved, however very little structural information can be gained fr
om the simple mass spectrum obtained. This disadvantage can be overcome by coupling ESI with tandem mass spectrometry(ESI-MS/MS). Another important advantage of ESI is that solution-pha information can be retained into the gas-pha.
Ionization mechanism: The liquid containing the analyte(s) of interest is disperd by electrospray,into a fine aerosol. The aerosol is sampled into the first vacuum stage of a mass spectrometer through a capillary carrying a potential difference of approximately 3000V, which can be heated to aid further solvent evaporation from the charged droplets. The solvent evaporates from a charged droplet until it becomes unstable upon reaching its Rayleigh limit. At this point, the droplet deforms as the electrostatic repulsion of like charges, in an ever-decreasing droplet size, becomes more powerful than the surface tension holding the droplet together. At this point the droplet undergoes Coulomb fission, whereby the original droplet 'explodes' creating many smaller, more stable droplets. The new droplets undergo desolvation and subquently further Coulomb fissions. During the fission, the droplet los a small percentage of its
mass (1.0–2.3%) along with a relatively large percentage of its charge (10–18%).
There are two major theories that explain the final production of gas-pha ions: the ion evaporation model (IEM) and the charge residue model (CRM).
厦门航空空姐The ions obrved by mass spectrometry may be quasimolecular ions created by the addition of a hydrogen cation and denoted [M+H]+, or of another cation such as sodium ion, [M+Na]+, or the removal of a hydrogen nucleus, [M−H]−. Multiply charged ions such as [M+n H]n+are often obrved. For largemacromolecules, there can be many charge states, resulting in a characteristic charge state envelope. All the are even-electron ion species:electrons(alone) are not added or removed, unlike in some other ionization sources. The analytes are sometimes involved in electrochemical process, leading to shifts of the corresponding peaks in the mass spectrum. This effect is demonstrated in the direct ionization of noble metals such as copper, silver and gold using electrospray.
Applications: Electrospray is ud to study protein folding.Additionally, ESI-MS is ud to test for the prence of nano clusters, for example U-60.Generally, ESI-MS application includes: Liquid chromatography-mass spectrometry(LC-MS);Capillary electrophoresis-mass spectrometry(CE-MS);Noncovalent gas pha interactions.
