CHEM202 Final

In reverse phase chromatography, the stationary phase is... a.polar b. non-polar c.either non-polar or polar d. ionic

b

In gas chromatography, the concentration of a substance can be determined by ... a. measurement of the height of the peak produced by the substance. b. comparison of the Rt of the substance with that of a standard. c. comparison of the area under the peak produced by the substance with the areas under the peaks produced by standard solutions. d. calculation of the Rt value of the substance.

c.

Enantiomeric compounds: a. Have different melting points b. Have different boiling points c.Interact differently on silica gel d.Have the same physical properties and cannot be separated

d.

Bromine possesses two isotopes (79Br and 81Br) in an approximate 1:1 ratio. In the mass spectrum of Br2, how many peaks will the parent ion contain? a. 79 b. 81 c. 4 d. 3 e. 2 f. 1

e.

Chromatography cannot be used to purify volatile substances.

False

Four organic compounds were separated by silica gel column chromatography with benzene as the eluent. 2-butanone, pentane, butanol, propanoic acid What is the order of elution from the column? a. 1. pentane 2. 2-butanone3. butanol4. propanoic acid b. 1. propanoic acid2. 2-butanone3. butanol4. pentane c. 1. propanoic acid2. butanol3. 2-butanone4. pentane d. pentane2. 2-butanone3. propanoic acid4. butanol

a

In order to remove highly charged compounds from an ion exchange column, the elution solution should be high or low ionic strength? a.High ionic strength b.Low ionic strength

a.

Sample A is made up of two components, O and P. A small sample of sample A was dotted onto a tlc, and a chromatogram was developed using an appropriate solvent. The result is shown below. (P is closer to solvent front) Component O is adsorbed ... a. more strongly onto the stationary phase and has a smaller Rf value than component P b. less strongly onto the stationary phase and has a larger Rf value than component P. c. more strongly onto the stationary phase and has a larger Rf value than component P. d. less strongly onto the stationary phase and has a smaller Rf value than component P.

a.

You synthesize a liposome sample and analyze it by DLS. You then run the sample through an extruder. What is the most likely scenario, before and after? a. Before: diameter = 1200 nm; polydispersity = 0.35; after, diameter = 300 nm; polydispersity = 0.15 b. Before: diameter = 1200 nm; polydispersity = 0.15; after, diameter = 300 nm; polydispersity = 0.35 c. Before: diameter = 300 nm; polydispersity = 0.15; after, diameter = 1200 nm; polydispersity = 0.35 d. Before: diameter = 300 nm; polydispersity = 0.35; after, diameter = 1200 nm; polydispersity = 0.15

a.

You want to separate two proteins, Protein A has a MW=34 kDa and the Protein B has a MW=98 kDa. Using size exclusion column, predict the order of elution. a. Protein B then Protein A b. Protein A then Protein B c. Both will elute at the same time in size exclusion. You need to use affinity chromatography to separate proteins. d. You can't predict without knowing the polarity of the proteins also.

a.

Your purification strategy of combinations of chromatography steps gives a protein preparation with a single band on SDS-PAGE. Which of the following would be best for determining the protein concentration (as mg/ml or molarity)? a. Measure a UV absorbance scan and use the absorbance at 280nm with the molar extinction coefficient (predicted from the amino acid sequence) b. Determine amino acid composition after hydrolysis to amino acids c. Colorimetric assay using Bradford or BCA assays d. "Guesstimate" the concentration from the intensity of bands on SDS-PAGE gels

a.

A mass spectrometer is often linked to a gas chromatogram (GC). This is done so that the ... a. gas used as the mobile phase in the GC is first purified by the mass spectrometer. b. substances can be separated in the GC and then the mass spectrometer can be used to analyze the mass of each pure compound. c. exact mass of the mixture is determined by mass spectrometry before it is passed into the GC. d. substances can be separated in the mass d. spectrometer and then passed through the GC for analysis.

b.

A student used an ion exchange resin with an -NR3+1 group. A mixture of 3 transition metal complexes (below) was eluted through the column. A. K3[Cr(ox)3] . 3H20 B. [Co(NH3)4CO3]NO3 C. K[Co(EDTA)]2H2O Which order will these compounds elute from the column? a. ABC b. BCA c. CAB d.ACB e. BAC f. CBA

b.

Select the true statement about fluorescence spectroscopy of molecules in the UV-visible region. a. Emission usually occurs at energies that are greater than the energies of excitation b. Emission usually occurs at energies that are less than the energies of excitation c. Emission usually occurs at energies that are equal to the energies of excitation. d.None of the above is accurate

b.

The doubly charged (i.e. doubly protonated) peptide VKEGMNIVEAMER was analyzed by mass spectrometry. The mass of this peptide is 1448 g/mol. The molecular ion should have m/z ratio of .... a. 1448 b. 724 c. 2896 d. 965

b.

Thin layer chromatography can be used to distinguish between different molecules. If a particular molecule has low solubility in the mobile phase used, then it ... a. will move at a speed close to that of the solvent. b. will have a low Rf value. c. must have a high molecular mass. d. will spend more time dissolved in the mobile phase than attached to the stationary phase.

b.

When a mixture of proteins is separated by gel filtration, a. the smallest molecular weight protein is eluted first. b. the largest molecular weight protein is eluted first. c. the most polar protein is eluted first. d. the most non-polar protein is eluted first. e. the most positively charged protein is eluted first. f. the most negatively charged protein is eluted first.

b.

Which of the following compounds can be characterized by UV-Vis spectroscopy? a.hexaaquaaluminum complex ion, [Al(H2O)6]3+ b. trans-1,2-dibenzoylethylene c. Chromium (Cr) d. penta-1,4-diene

b.

Which of the following peaks would be diagnostic for the IR spectrum of diethyl amine? a. two sharp peaks at 3300-3400 cm-1 b. one sharp peaks at 3300-3400 cm-1 c.two sharp peaks at 2700-2900 cm-1 d. one broad peak at 1600 cm-1

b.

A student used an ion exchange resin with an SO3-1 group. A mixture of 3 transition metal complexes (below) was eluted through the column. A. [Co(NH3)6]Cl3 B. [Co(NH3)4CO3]NO3 C. K[Co(EDTA)]2H2O Which order will these compounds elute from the column? a. ABC b.BCA c.CBA d. CAB e. ACB f. BAC

c.

Two solutions of the same compound were made up. Solution A was of concentration 0.98 × 10-4 mol dm-3, and solution B was 1.66 × 10-2 mol dm-3. The UV spectrum of solution A contained one absorption at λmax = 230 nm, while the spectrum of solution B contained absorptions at λmax = 230 and 365 nm. The difference in the spectra was because: a. the value of λmax depends on concentration. b. electronic spectroscopic data are not always reproducible. c. εmax for the absorption at 365 nm is much smaller than εmax of the band at 230 nm d. the value of εmax depends on concentration

c.

Which of the following statements about mass spectrometry is incorrect? a. Isotopic distribution patterns are observed in mass spectra. b. Mass spectrometry gives information about fragmentation patterns which can be compared to reference spectra. c. Mass spectrometry provides direct information about complete structure and connectivity d. Parent ions (the molecular weight) are not always observed in the mass spectra of compounds.

c.

Affinity chromatography separates based on... a. the attachment to the column matrix of ionic groups known that bind to the wanted protein. b. separates proteins on the basis of charge c. separates proteins on the basis of size d. separates proteins on their ability to bind to specific groups on the column matrix. e. proteins can be selectively eluted by solutions of different hydrophobicities or ionic strengths.

d.

Fluorescence probes... a. are highly fluorescent reagents that are designed to bind strongly and specifically to certain targets b. are reagents used to probe biological systems in specific sites. c. enable the use of fluorescence for the detection of molecules that are not fluorescent d. all of the above

d.

Liposomes are... a. micelles b. a bilayer of hydrophilic molecules c. a bilayer of hydrophilic molecules d. a spherical bilayer of amphiphilic molecules e. a cell membrane

d.

The following compound was isolated off of a column: It's literature optical rotation value is - 44° The calculated optical rotation value is - 22° What is the optical purity of this sample? a. Cannot be determined from this information b. 100 % c. 75 % d. 50 % e.25 %

d.

Which of the following methods could be used to check the molecular weight of a purified protein? a. SDS-PAGE b. Mass Spectrometry c. Analytical Size Exclusion d. Chromatography d. All of the above

d.

Which of the following types of chromatography involves the separation of substances in a mixture over a 0.2mm thick layer of an adsorbent? a. gas chromatography b. column chromatography c. affinity chromatography d. TLC (thin layer chromatography) e. ion exchange chromatography

d.

In chromatography, there are two phases, a stationary phase and mobile phase. The stationary phase can be solid or liquid supported on a solid. What is the mobile phase? a. solid b. liquid c. gas d.solid or liquid e. liquid or gas

e

To elute target proteins from an affinity chromatography matrix, which of the following conditions would be the most appropriate? a. Low salt concentrationS b. High Salt concentration c. Low pH d.High pH e. Adding a soluble ligand which competes with the affinity tagged protein for binding to the column f. just keep washing buffer through the column, isocratic elution

e.