ExamIReviewSummer2010HandoutsBW

ExamIReviewSummer2010HandoutsBW - Lab Basics! Units!...

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1 Lab Basics • Units • Signifcant Figures /Precision • Pipeting • Spectroscopy Units • Understand Conceptually – Molar = moles/liter, moles o± solute per total volum – mM, μg/aliquot – Protein Assay: mg/ml, all types [protein] – Enzyme Assay: units/ml, activity conc. – Ammonium sul±ate % saturation • Not the same as % W/V • Not a concentration. Signifcant Figures • Report to the “highest/frst” place o± uncertainty. • Singlets: Instruments precision • Replicates: Reproducibility n = number or values (p. 9 in lab manual) Set of 2 values 125.2 123.1 125.2 123.1 121.2 127.4 122.8 More than 2 values Look for first place of uncertainty Average 123.94 lbs. Frequency σ - designates the range in which ~68.3% of the values fall near the average.
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2 Signifcant Figures • Adding/Subtracting two values (LDH LAB 3) – Add errors directly. – e.g. 10 ± 5 g + 1.0 ±0.5 g = 11 ± 5.5 • 11 ± 6 • Multiplication/Division (LDH LAB 1) – Add percent errors (Conservative method) – e.g. 10 ± 1 g / 100 ± 1 ml • Both have 1% errors. Final error = 2%. • Final error: 0.1 g/ml x 2% = 0.002 g/ml • 0.100 ± 0.002 g/ml Propagation o² Errors: Purifcation Table • Multiplicative ²unctions – percent errors. • Will be help²ul ²or progress report I. Error Propagation will not be tested on exam I. Reproducibility Accuracy Poor Good Poor Good Good Good Poor* Poor * Poor Accuracy - does not measurably hit the target! Reproducibility Randomness: ex) technique, spec error. Corrected only by more repeats Can a²²ect accuracy but could be corrected with more replicates. Defnes optimal range in quantitative assays. Direct Spec Assay/Beer’s Law Protein Assays Standard curve Enzyme Assays optimal slopes Accuracy Randomness ex) technique, spec error. Can be corrected with replicate measurements. Systematic Errors Each sample a²²ected the same way. Could be corrected when recognized. Best in the optimal range o² assays Systematic Error could shi²t optimal range.
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3 Systematic Shift Error or Not? temperature • Standard curve normalizes – estb. optimal range of incubation. • Error – incubated longer than hour.
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This note was uploaded on 10/07/2010 for the course POLI SCI 40 taught by Professor Sch during the Spring '10 term at UCLA.

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ExamIReviewSummer2010HandoutsBW - Lab Basics! Units!...

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