Scientific references

The tables a bench looks up. The figures are the usual reference values. Check a critical mass or a pH on the bottle and with a meter. The calculations sit in the calculators.

Periodic table

Pick an element. The molar mass is the one the molarity calculator uses. A number in brackets is the mass number of a long-lived isotope.

SI prefixes

The prefixes a lab uses most.

Symbol	Name	Factor
T	tera	10¹²
G	giga	10⁹
M	mega	10⁶
k	kilo	10³
m	milli	10⁻³
µ	micro	10⁻⁶
n	nano	10⁻⁹
p	pico	10⁻¹²
f	femto	10⁻¹⁵

Constants at the bench

The SI values, rounded the way the bench uses them.

Constant	Value
NA	6,022 × 10²³ mol⁻¹
R	8,314 J·mol⁻¹·K⁻¹
F	96 485 C·mol⁻¹
0 °C	273,15 K
Vm	22,4 L·mol⁻¹ at 0 °C and 101,325 kPa

Amino acids

Average residue mass in a protein chain, in dalton.

Code		Residue mass (Da)
Ala	A	71,08
Arg	R	156,19
Asn	N	114,10
Asp	D	115,09
Cys	C	103,14
Gln	Q	128,13
Glu	E	129,12
Gly	G	57,05
His	H	137,14
Ile	I	113,16
Leu	L	113,16
Lys	K	128,17
Met	M	131,19
Phe	F	147,18
Pro	P	97,12
Ser	S	87,08
Thr	T	101,11
Trp	W	186,21
Tyr	Y	163,18
Val	V	99,13

Nucleotides

Residue mass in a chain, in dalton.

Base	DNA	RNA
A	313,2	329,2
C	289,2	305,2
G	329,2	345,2
T / U	304,2	306,2

Buffer pKa at 25 °C

The same pKa values as the buffer calculator. The useful window sits about one unit around the pKa.

Buffer	pKa	Useful range
Tris	8,07	7,1–9,1
HEPES	7,48	6,8–8,2
MOPS	7,20	6,5–7,9
Phosphate	7,21	5,8–8,0
PIPES	6,76	6,1–7,5
MES	6,15	5,5–6,7
Acetate	4,76	3,6–5,6

Temperatures at the bench

Usual set-points. Not a rule.

Where	Temperature
Ice bath	0 °C
Room	20–25 °C
Incubation, body	37 °C
Heat shock	42 °C
PCR, denaturation	95 °C
PCR, extension	72 °C
Autoclave	121 °C
Freezer	−20 °C
Ultra-low	−80 °C
Liquid nitrogen	−196 °C