Project:OD600 Measurement

The idea is to take a 600 nm source, (or a source including 600 nm and a BP filter) and a level detector, and calibrate it to match 0.4 at OD600 on a proper spectrophotometer..

The initial attempt was to use a white led with a filter for something approximating 600nm

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At the moment the main issue is that the LDR (light dependent resistor) only sees about 20 ohms of difference between the initial inoculation and the mid-log phase, which shows as 0.4 OD600 on a spectrophotometer.

If you don't have access to a spectrophotometer, (or even if you do), this should be a convenient way to estimate OD600 values for your sample

A secondary project is to cast some 10mm x 10mm resin blocks to be used for calibration against a system that takes a cuvette.

Here is a document describing various methods for calibrating spectrophotometers;

http://www.perkinelmer.co.uk/CMSResources/Images/44-136839TCH_Validating_UV_Visible.pdf

alternative ideas

use a stain that binds to a protein that is only expressed during exponential growth phase

DNA Pol II is only expressed during the stationary period of growth, and so might be used as a marker for the end of exponential growth

omp regulates response to osmolarity is expressed in postexponential phase; (Connell et al 1987)