Units and Concentrations

Units

• There are three types of units in pyplate:

  • Mass (grams, g)

  • Volume (liters, L)

  • Numbers

    • moles (mol)

    • Enzyme Activity units (U)

PyPlate supports these common prefixes:

‘p’ (pico) ‘n’ (nano)

‘u’ (micro) ‘m’ (milli)

‘k’ (kilo) ‘M’ (mega)

Quantities are specified as strings with a number and a unit abbreviation. (‘1 mmol’, ‘10.2 g’, ‘10 uL’, …)

Concentrations

Concentrations can be defined in terms of molarity, molality, or ratios of units:

Examples (‘w’ stands for weight, ‘v’ stands for volume, ‘%’ stands for per hundred):

‘0.1 M’ ‘0.1 m’ ‘0.1 g/mL’

‘0.01 umol/10 uL’ ‘5 %v/v’

‘5 %w/v’ ‘5 %w/w’

Note

For ‘%w/v’, the units are defined as default_weight_volume_units in the configuration file. (The default is ‘g/mL’)

Unit Usage within PyPlate

• The fundamental unit for liquids and solids is moles.

  • Mass is calculated using the molecular weight of the substance.

  • Volume is calculated using the density and molecular weight of the substance.

• The fundamental unit for enzymes is enzyme activity units (‘U’).

  • Enzymes must be defined in terms of activity units per mass. (specific_activity)

  • specific_activity can be defined in terms of U/g or g/U

• Masses and volumes are considered to be strictly additive.