Topic 1 Tools of the Biology Laboratory Exercise I. The spectrophotometer. Exercise II. Liquid Measurements. Exercise III. Sedimentation and Centrifugation.
Bio 185 Labs: goal When: Self-paced: Lab-Report:
Bio 185 Labs: set-up.
Exercise I. The Spectrophotometer Experiment 2: Absorption Spectra of Dyes. Experiment 1: Concentration of an unknown Dye.
Exercise I. The Spectrophotometer
Spectrophotometry:
Exercise I. The Spectrophotometer
Spectrophotometry: You need to “Blanc” the spectrophotometer for each solvent and change of wavelength.
Exercise I: Experiment 2: Absorbance spectrum:
Absorbance spectrum:
Exercise I. The Spectrophotometer: Absorption spectrum. 1. Change wavelength. 2. Blanc. 3. Measure.
Exercise I. The Spectrophotometer: Absorption spectrum.
What wavelength to determine the concentration of a solution?
Exercise I. The Spectrophotometer: Concentration of an unknown dye. Standards of known protein concentration Optical density of solutions with unknown concentration.
LAB REPORT FORMAT: (1 report per group!) LAB TITLE: Concentration of a dye. Experiment 1. Goal: one sentence. Method: Relevant. Results: (based on class data). A (mean and SEM) is significantly different (P<0.05) from B (mean and SEM). Conclusion: A is different from B. Explanation.
Figure 1. Standard curve of yellow dye at 420 nm. We measured the optical density at 420 nm of four concentrations of yellow dye (1, 2, 3, and 4 drops per sample) using a Spectronix 21 spectrophotometer. The OD of Standard 1 ((0.217 ± ) was significantly smaller (P<0.05, Student’s t-test) than that of Standard 2 (0.410 ± ), the OD of Standard 2 was significantly smaller (P<0.05) than that of Standard 3 (0.619 ± ) and the OD of Standard 3 was significantly smaller (P<0.05) than that of Standard 4 (0.806 ± ). We calculated the standard curve (linear regression y = x , R 2 = ).We measured the optical density at 420 nm of an unknown concentration of yellow dye (OD equals ± ) and used the standard curve to determine its concentration (3.44 drops per sample).
Exercise II. Liquid Measurements Accuracy of (1) 100 ml Graduated cylinder, (2) 10 ml serological pipette, and (3) 1.0 ml micropipette. Percent error when device is used at maximal and 1/10 th maximal nominal volume.
Exercise II. Liquid Measurements Measure by weight (mass). Read mass in g. Tare or zero the balance. Add volume of water. Measure. What mass (g) do you expect?
Exercise II. Liquid Measurements: 50 ml cylinder.
Exercise II. Liquid Measurements: 10 ml pipette.
Exercise II. Liquid Measurements
Exercise II. Liquid Measurements: 1.0 ml micropipettor.
Exercise II. Liquid Measurements
Exercise III. Sedimentation and Centrifugation.
Sedimentation at 1 gSedimentation in 50 ml conical tube at slow centrifugation Sedimentation in microfuge tubes at high speed centrifugation
Exercise III. Sedimentation and Centrifugation.
Exercise II. Liquid Measurements
Exercise III. Sedimentation and Centrifugation.
Microscope:
Exercise III. Sedimentation and Centrifugation. Sedimentation at 1 gSedimentation in 50 ml conical tube at slow centrifugation Sedimentation in microfuge tubes at high speed centrifugation