Upsala, January 27. 1935. pear fi ofessor Heiaelberger. E'irst I wish tc; thank you for your letters of hovember 30th and December l3tn. I have not yet dct tne suple of lipoid-free thyrGglObUlin frcm Dr .Cavett, so I woncler if he has had a suple ready. I nwe alscussecl your prcycsal of aividiu tne work over two ar- ticles wita prcf'esscr Sveuberb, but is he thought it just as good to keep the whcle inside cne axtiole , but he proposed to change the cronc- lodical order cf the difzer-ent divisions in tae way I have dcne now in the YS; ne found it &ore natural to have the iacelectric pcint section before tne centrifwe work. we found it necessary to extend the sectiGn about the sedimentation constat SGlZleWhat, anu I found it necessary to recalculate the run no: 20, because it was quite obvious tnat there were tqo components present Which could be calculated 8eparately. Professor YvedWi& has added tne sua11 note just before wsurrrmaryw about tae &rants, becaase the whole expenses connected with the centtrl- fu&e$ are paia fro& these grants. The v;clue for tne molecular weight I gave YOU in my letter or NO- veruber 19th is not correct, tne correct value is about 650-700 000, but yc;u only &et this value, when the concentration is higher than + $i below this conceatraticn there is a rather strcng aissociaticn tahiry place o We aid not find this error (in tae measureuents ), before we got the value8 calculatedl f'cil: a second wavelendth, then the values for tne concentrhtion Gradient in the cell wc;ula not at all ccrrespona, and we had tc control all the old measurerrents, ala then we found that there was a verj bid error in one of' the f'unaauental measureaenta (0,3 mm, tnat is equal to a Whole turn on the dial on the measuring microscope) in 4 of tne calculated 6 equilibrium ruris. These measueuents were made by a new &rl we had to assist miss horling, but we nad he only for & sncr t tiue , because sbe was quite inpcmible for these measureaents. When we tnen Gcjt tile equilibriu runs zecalculatea, they Showed a very 8trc;q arix't in tne values for the lower concentrations as you see in the equilibriuu fun tables, but at tne concentrations from about + 9 ana upwaras tne calculbted molecular weist seems to De ratner constant; yet the tnyroglobulin is always containing sme bi@er molecular compo- nents * Unues taese conciitims (strong ana 6nanging aissociation and more urc;leculu syec;ies) it is not allowed (as I told you here in upsala) ?' to use the expression we First used f'or the preliuiinary calculation of equilibrium run8 riCi.1, but the utncd I have aerived fcr tne calculation ox' tne aolecular weight 18 also not so sure in this case as it will usually be, because one has to extrapclate tne concentration curve quite A bit uue tG tue impossibility (caused by the hi@ molecular co&- porient) cf ma8uriry tfie plate quite aown to the bottom of the cell. Tnis mans mat tne errw in these equilibriu runs could perhaps be sC;u +LO p, but tne values'diven itl'e probably rather too 10s than too yLig. In case clf tat: dilute solution these equilibrium runs are rather uncertain, so that they cannot Give any informatlons about the size and mount of' tne uissocibtion prclaucts. Tne seaiwutation velocity runs - ". I- __ - *n- " - --_ - I" ~ . _- -_____ ----- --- -.....w-.----.*II____" I ___ " -- tell us toc trrbt there is a strok dissociation takin$ place, when the concentrations deirebse below p p. This dissociation is causing the strongly aloping baseline you generhlly fGUd in tae velocity runs, where you in nearly ail tfie experiuents used a concentration much lower than + (&YOU ~,17 20); in the single run, no.17, with a higher con- centration the slopiry baseline na8 uisappeared. I pxopose that we in- . troduce two more Figures (no.3 and 4) snowing tne pnotometer curves of' tue twc, run8 no. 17 ma 14. You Would pernaps be so kind as tc; get these and tne electropurorek3e figare arawn like tne fid.2, SG that tney may be cbl interest, but I nae not introduced anythin.& about tnis in tne MS, because I tnink it much better7 if you yc-uself uke the necessary change in WDisc.ussionn. The shll alterations made in this part me made by &ressa SveaberG. YOU see, it is very easy tc, get quite a number or uifferent nemL;yains with botn bigher ana lower molecular weights. In "Discussion" I taink tnbt the part wnere you speak about the ola preparations ShGUlU pernaps ue awed scmewhat; it is correct that the seaiuntr;ttion cbnstant of the main comuonent is the same, but this win ccuyonent is ju;it Lmzumxa in old preparations a much sualler part or the total protein piesent, especialLy in tne csL8e of the hman thp- &;lobulin, wnicn inuicates that a Uage in the protein (taken as a wnole) is takir& plhce. It woulu pernaps be possible just by a new pre- cigitatlon GI the thyro&lobulin to &et a new preparation quite as homoa Genecius as the freshly preyaed tnyro&loUulln. I wmaer if' one can say UtLt thyrc&lobulin has an unusually low isoelectric point o Tiselius hbs fcund the .iscelectric point for horse seru albuin at yi-i 4,6&, by kter aeteiiuinaionB nealy tu saw or pernaps a little lciwer vblue. Tne aorse sera globu- 1 have always found lin fibs isbelectric pcint cf about ph 5,59 but we know nothing about the isoelectric pcint for the noel; albimin ar~d dlobulin, and they may be lower tau tnose of the horse; I have veiy cften thought of nibking the is6electric ycint ueterruinatians on quite a lot c;f serum albumins and glcibulin8 f'rch uirferent species, but sci far I nave nct Got tne time tG a6 SC. I realLy tnink tnbt tais wwk cn the tnyro&obulin has been very intereatiw uci tLbt it Lu@t to be ccntindeci on aifferent phrtS, but I iLlri afraid tn;lt it WCUld be too 10% now tG StWt a discussion With you bbout tnbt, but pernaps 80- cf' your asistats are later on coniind tc Upsah? I nbve for6ctten tc; am& Profesam Sveaberg whether he has abde any hrrage~ents witn yc;u izs rt3gard to tne reprints; generblky they want to get (or buy) 200 exp. f6r We institute. Would you please be SO kina to ccrrect at least tne en&ish in tne plhces in tne An8 I nave written? I regret very much that we can't nave tne possibility of' aiscussing the whole MS together per scinally, timt wo-uia nave been very interesting. At last I wisn to be6 ycu to excuse nie for havind been sc late wbth tne W. Witra uy kinaest regardB to you itna Us.HeiueLberger, 8 ince r e ly 0. Pede-.