Table Of ContentEncyclopedia of Biophysics
Gordon C. K. Roberts
Editor
Encyclopedia of Biophysics
With1597Figuresand131Tables
Editor
GordonC.K.Roberts
HonoraryProfessorofBiochemistry
DepartmentofBiochemistry
UniversityofLeicester
Leicester,UK
ISBN978-3-642-16711-9 ISBN978-3-642-16712-6(eBook)
ISBN978-3-642-16713-3(printandelectronicbundle)
DOI10.1007/978-3-642-16712-6
SpringerHeidelbergNewYorkDordrechtLondon
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To Hilary
Preface
PerhapsthefirstissueinintroducinganEncyclopaediaofBiophysicsisthequestion
“What is Biophysics?”. The answer to this has varied considerably over time and
betweendifferent‘biophysicists’,particularlydependingonwhethertheyhavecome
tobiophysicsfromphysicsorphysiology.Forthepresentpurposes,wehaveadopted
thedefinitiongivenbytheNobelPrize-winningphysiologistA.V.Hill(Science124,
1233, 1956): Biophysics is “the study of biological function, organization, and
structure by physical and physicochemical ideas and methods.” – to which one
would now add methods of mathematical analysis and computer modelling. An
important feature of Hill’s definition is that it includes both physical methods and
physical ideas. The astonishing developments in physical methods over the last
hundredyearshavemadethemubiquitousinbiologicallaboratories–andindeedin
hospitals.However,toquoteHillagain“theemploymentofphysicalinstrumentsin
a biological laboratory does not make one a biophysicist - otherwise any user of
amicroscope,abalance.....orapHmeterwoulddropautomaticallyintothatclass.”
Beyondsimplytheuseofphysicalmethods,itisthecombinationofbothphysicaland
biologicalideas,intuitionsandexperiencethatmakesaBiophysicist.
The application of physical methods in biology has a very long history. For
example,AntonievanLeeuwenhoek(1632–1723)developedimprovedmicroscope
lenses which allowed him to be the first to observe and describe single-celled
organisms–thebeginningofmicrobiology.The18thcenturysawmuchspeculation
about ‘animal electricity’, culminating in the 1780s in Luigi Galvani’s famous
experiments on the relation of electricity to muscle contraction. The middle of the
19th century saw what was probably the first explicitly biophysical programme of
research,inwhichagroupofphysiologists(duBois-Reymond,Ludwig,vonBr€ucke,
von Helmholtz) proclaimed their intention to ‘reduce physiology to physics and
chemistry’.OfcoursethestateofphysicsatthetimewassuchastomakeBiophysics
averyprematureventure,butthisgroupdidmakeimportantdiscoveries,notablyin
physiologicalopticsandelectrophysiology,usingphysicalmethods. Anassociateof
this group, Adolf Fick – well-known for his law of diffusion – published what is
probablythefirstbiophysicstext,DieMedizinischePhysik(1856).
Inthe20thand21stcenturiesthere hasbeenadramatic floweringofBiophysics.
Theearlypartof20thcenturysawthedevelopmentofphysicaltoolswhicharenow
familiarinbiology–fromX-raydiffraction(vonLaue,Bragg)totheultracentrifuge
(Svedberg)andtheelectronmicroscope(Knoll&Ruska)–andthismethodological
development continues apace, notably with single-molecule techniques. The 1920s
and1930ssawthebeginningsofphysicochemical(Cohn,Edsall,Linderstrøm-Lang)
and structural (Astbury, Bernal, Hodgkin, Perutz) studies of proteins. At the same
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time, the first Departments or Institutes of Biophysics began to be established.
In Germany these were commonly focussed on the study of radiation effects on
organisms, while in the USA they concentrated largely on physiology. Many of
theselaterexpandedintootherareasofBiophysics,andmanymoreDepartmentsof
Biophysics – and Biophysical Societies – were established in the USA, Europe
and Israel in the 1940s and 1950s. The power of the Biophysical approach was
demonstrated unequivocally in the 1950s with the determination of the first three-
dimensional structure of a protein, the structure of DNA and the Hodgkin-Huxley
modeloftheactionpotentialinnerves.
Overthelast50years,Biophysicshascontinuedtodevelopatanastonishingpace.
Biophysicistsstudylifeateverylevel,fromatomsandmoleculestocells,organisms,
andenvironments.MolecularandCellularBiophysics:Thisisperhapsthepredom-
inantstrandofmodernbiophysics.Itincludes,forexample,structural,functionaland
simulation studies of macromolecules and macromolecular assemblies of ever-
increasing complexity and imaging of cells at ever-increasing resolution. Applied
Biophysics:Theapplicationsofbiophysicalmethodsareperhapsmostnotableinthe
areaofmedicalimaging-includingX-rayCATscans,magneticresonanceimaging,
positron emission tomography and ultrasound scans. Therapeutic applications
include radiation therapy of increasing sophistication and cardiac defibrillators.
Inadditiontomedicalapplications,therearenowincreasingandexcitingapplications
innanotechnology.EnvironmentalBiophysics:Formanyyearsanimportantareaof
biophysics has been the study of the effects of ionising - and indeed non-ionising -
radiation onorganisms. Another keyarea ofconsiderable current importance is the
developmentofmathematicalmodelsof,e.g.,heatandmasstransferatthelevelof
organismsandecosystems.
ThisEncyclopediaisintendedtoprovidearesourcebothforbiophysicistsinter-
estedinapproachesoutsidetheirimmediatesub-disciplineandforpeoplecomingto
biophysics from either the physical or biological direction. The emphasis is very
much onmolecular andcellular biophysics,butsome discussion ofimaging andof
nanotechnologyisincluded.Justasthereisoverlapbetweenchemistryandphysics,
sothereisoverlapbetweenbiophysicsandbiochemistry;ourfocusisofcourseonthe
techniques and uses of biophysics, but biochemical context is included where
appropriate.
TheEncyclopediaconsistsoftwokindsofentries,SystemsandTechniques.
• IntheSystemssections,biophysicalapproachestoparticularbiologicalsystemsor
problems–fromproteinstructuretomembranes,ionchannelsandreceptors–are
described. These sections, which have an emphasis on the integration of the
differenttechniques,thereforeprovideanentryintoBiophysicsfromthebiolog-
icalmorethanfromthetechnique-orientedphysicsdirection.
• IntheTechniquessections,eachofthewiderangeofmethodswhichfallunderthe
headingofBiophysicsareexplainedindetail,togetherwiththeirstrengthsandthe
limitations of the information each provides. Experimental techniques covered
range from diffraction, through a wide range of spectroscopic methods (X-ray,
optical, EPR, NMR), kinetics, thermodynamics and hydrodynamics, to imaging
(from electron microscopy to live cell imaging and MRI). The important and
increasingly powerful computational, modelling and simulation approaches are
alsoincluded.
Each of the Sections includes concise introductions to the major concepts and
methods, and outlines of more specific topics, in each case with links to a limited
Preface ix
number of carefully selected key reviews and/or papers in the scientific literature.
Extensive cross-referencing (hyperlinks in the online version) between different
articlesallowsaccesstorelatedtopicsinauser-friendlymanner.
TheonlineversionoftheEncyclopediaisintendedtodevelopcontinuously,both
bytheupdatingofexistingentriesandbytheadditionofnewarticles.Inthiswayit
willprovidetheresourcestohelpbothpractisingbiophysicistsandnewcomerstothe
fieldtokeeppacewiththecontinuingandexcitingdevelopmentsinBiophysics.
Leicester GordonC.K.Roberts
UK
May2012
