499
modulus≈1300 pN. Basepair rise 0. 34 nm/basepair. Helical pitch in solution 10.3–
10.6 bp.
Others:Microtubule: diameter 25nm,persistence length 1mm.Intermediate filament:
persistence length 0.1μm,diameter 10nm,typical length 5μm. Actin: diameter
7 nm;persistence length 3–10μm;bend stiffness, 8· 10 −^26 Jm
Neurofilament: persistence length 0.5μmMotors
Myosin:Myosin-II (fast skeletal muscles) speedin vitro,8μms−^1 ;force 2–5pN.Myosin-
V(vesicle transport): 0. 35 μms−^1 .Myosin-VIII, XI (cytoplasmic streaming in
plants): 60μms−^1.
Conventional 2-headed kinesin: step size, 8nm; fuel consumption, 44 ATPs−^1 per
head; stall force, 6–7pN;speed in vitro, 100 steps/s=800nm s−^1 ; processivity,
100 steps/release
E. coli flagellar motor: Rotation rate 1200 protons/revolution, 100 revolutions/s;
torque, 4000pN nm.
F1 ATPase motor:Stall torque, 100pN nm;torque generated against frictional load in
Yoshida/Kinosita experiments, about 40pN nm.
RNA polymerase: Stall force, 25pN.Speed: E. coliPolI,1 6 basepair/s;Pol II, 0.05
times as great; Pol III, 15 times as great; Eukaryotic polymerase, 50 bp/sec; T7 virus
polymerase, 250 basepair/s
DNA polymerase: Stall force 34pN.Speed 1000 nucleotides/s (bacteria);
100 nucleotides/s(eukaryotic cells).
HIV reverse transcriptase:20–40 nucleotides/s.Ribosome: 2 amino acids/s(eukaryotic
cells) or 20s−^1 (bacteria).Genome
Bacteria, 1–5· 106 basepairs (1–5 Mbp); yeast, 12 Mbp; flatworm, 100 Mbp; human,
3200 Mbp. (For diploid organisms, like humans, double these figures to get the total
DNA in the cell.)
HIV, about 10 000 basepairs (10 Kbp), nine genes in different reading frames.
Lambda phage DNA 48.5 Kbp, so contour length≈ 16. 5 μm
Longest human chromosome 8cm,or0.25 Gbp.Neurons
Pumps:≈ 102 ions/sec/pump
Carriers:≈ 104 ions/spercarrier
Channels: ≈ 106 ions/sperchannel; density of sodium channels in squid axon,≈
300 μm−^2 ;unit conductance of open channel,GNa+=25pS=2. 5 · 10 −^12 Ω−^1.
Resting conductance per area, squid giant axong^0 tot≈ 5 Ω−^1 m−^2 ;individual resting
conductances followgK+≈ 25 gNa+≈ 2 gCl−. During an action potentialgNa+mo-
mentarily increases by about a factor of 500.
Capacitance per area≈ 1 · 10 −^2 Fm−^2