1975 a model for the origin of stable protocells in a primitive alkaline ocean

8/7/2019 1975 A Model for the Origin of Stable Protocells in a Primitive Alkaline Ocean

1/8

222

B i o S y s t e m s7 (1975) 222--229 North-ttolland Publishing Company, Amsterdam - Printed in The Netherlands

A MODEL FOR THE ORIGIN OF STABLE PROTOCELLS IN A PRIMITIVEALKALINE OCEAN

W.D. SNYDER and SIDNEY W. FOXI n s t i t u t e f o r M o l e c u l a r a n d C e l lu l a r E v o l u t i o n a n d D e p a r t m e n t o f C h e m i s t r y, U n i v e r s i t y o fM i a m i , 5 2 1 A n a s t a s i a Av e n u e , C o r a l G a b l e s , F lo r i d a 3 3 1 3 4 , U S A

When a mixture of the eighteen proteinous amino acids are suitably heated in the dry state with seawater salts,a copolyamino acid results. One fraction of this polymer is found, through isoelectric focusing, to consist of amixture of acidic and basic proteinoids, each of sharply limited heterogenei ty. When one fraction of the seawaterproteinoid is dissolved in hot water, and the solut ion is cooled, proteinoid microspheres result. These have

properties in common with simpler types, but are also stable at pH values to 9, in common with microspheresprepared by mixing acidic and basic proteinoids. These processes thus constitute a simple model for the origin ofa protocell stable in a primitive alkaline ocean.

A model for the origin of reprod ucing proto-cells (Fox, et al., 1967; Hsu, et al., 1971; Fox,1973a, Hsu, 1974) on Earth requires a prioraccumulation of amino acids in locales on thesurface of the primitive planet.

Experiments designed to simulate subse-quent polymerizat ion of the amino acids [oralternatively, (a) evaporation of solvent waterand (b) polyme riza tion of the dried amino acidresidue at the same temperature] at 70--200C(Harada and Fox, 1965; Young, 1965; Fox andHarada, 1960) have yielded a variety of pro-teinoids (copolyamino acids). Many of theproteinoids assemble easily in aqueous solutionto for m microspheres (Fox, 1968). The numer-ous protein-like properties of proteinoids andcell-like properties of the microspheres havebeen described elsewhere (Fox and Dose,

1972). The results are consistent with the viewthat the formation of proteinoids (preprotein)on the primitive Earth was frequent and rapid.

The enzymelike activities that have beencatalogued for thermal proteinoids {Fox,1974a) have been studied especially in acidicproteinoids, which are rich in aspartic acidand/ or glutamic acid, and in basic proteinoids,which are rich in lysine (Rohlfing and Fox,1969). The observed variations in arrays ofactivity are a function of the amino acid com-

position. However, the assembly and stabilityof the microspheres from any one kind ofprotein oid is limited by pH.

Acidic proteinoid alone forms enormousnumbers of microspheres at pHs below 6 butthe spherules dissolve at higher pH. Micro-spheres from neutral proteinoid tend to bestable at pHs as high as 7, but dissolve abovethat value. Basic proteinoid is quite soluble inwater, but addition of sodium chloride to thesolution results in microspheres stable up to pH12 (Rohlfing, 1975). A combi nati on of acidicand basic proteinoids yields "mixed" micro-spheres that are stable up to pH 8.5, and alsostable in acidic solution (Fox and Yuyama,1963). The microsphere of mixed proteinoidswould require independent syntheses of acidicand basic protein oids (presumab ly preceded by

some fractionation of amino acids into acidicand basic types), followed by subsequent trans-port and mixing, prior to assembly into mixedmicrospher e systems.

Such a sequence of special fractionations isno longer conce ptual ly required. Therm al poly-condens ation of amino acids in the presence ofseawater salts has been found to yield a singlepolymer that contains both acidic and basiccomponents, as determined by isoelectric fo-cusing. On treatment with water, this "sea-


2/8

water proteinoid" then forms microspheresthat are stable over a broader and higher pHrange than previously observed for proteinoid

microspheres (Fox and Dose, 1972). As notedin preliminary reports of work with seawaterproteinoid, similes processes could have oc-curred in primitive lagoons (Fox, 1973; Snyderand Fox, 1973).

The limited heterogeneity observed in theseawater proteinoids reflects similar findingsfrom this and other laboratories (Dose andRauchfuss, 1972; Saunders and Rohlfing,1972; Fox, 1974a) on other thermal poly-amino acids.

1. Experimental

1.1. Materials

Acrylamide, N,N'-methylenebisacrylamide(BIS), N,N,N,N'-tetramethylenediamine(TEMED), and an: mon ium persulfate were ob-tained in electrophoresis grade from EastmanKodak Co. Ampholine carrier ampholy tes, pH3-10, were purchased fro m LKB Product or AB.All other chemicals were reagent grade andwere used as purchased without further purifi-cation.

1.2. Methods

1.2.1. Artificial SeawaterOne 1 of trace MBL Fo rmul a (Cavanaugh,

1956) artificial seawater was prepared by com-bining 24.72 g NaC1, 0.62 g KC1, 1.36 g CaC12 2 HOH, 4.66 g MgC12 6 HOH , 6.29 g MgSO4 7 HOH, 0.089 g KBr, 0.003 g NaF, 0.037 g

SrC12 6 HOH, 0.0 24 g H a BO s a nd d ilu ting tovolume. Sodium bicarbonate (0.180g) wasadded ju st before r.se.

1.2. 2. Seawater ProteinoidThe synthesis of the seawater proteinoid was

set up to model a two step process of (a)evaporation of the water in a geologicallyaqueous solution followed by (b) polymeriza-tion of the dried amino acid residue at the sametemperature employed for evaporation. [The

223

elevated temperature and dry state of the solidare required for ther mody nami c reasons (Foxand Dose, 1972; Fox, 1974b)].

Fifteen grams of the eighteen com mon (Fox,et al., 1970) L~-amino acids in equimolarproportions was slurried in 375 ml of artificialseawater (4% slurry). The slurry was evapo-rated to a thick paste, and heated under nitro-gen flow in a 190C oil bath for 7 hr. The finalreaction mixture temperatur e was 180C. 1The crude pr oduc t was an orange-brown friablesolid (22 g). Eleven grams of the product wasslurried in 100 ml of water and the suspensionwas dia lyze d with stirring against seven changes

of 400 ml of water each. The first dialysisoccupied 6 hr while the n ext five each spanned24 hr. Appr oxim ate ly 20 mg of NaN3 wasadded at each change to prevent microbialgrowth. Combine d diffusa tes and filtered re-ten tat e were lyophil ized; undissolved solidswere dried over P205 (20 mm Hg).

The composition of amino acids employedreflects what could have happened in a com-plex matrix; it does not indicate the exactnature of a primitive mixtur e of amino acids.

1.2. 3. Neutral P roteinoi dNeutral protei noid was prepared as de-

scribed (Fox and Waehneldt, 1968, no. 55).The procedure is essentially identical to thatfor seawater proteinoid except that salts wereomitted.

1.2. 4. Microsphere sA 4% (40 mg/ml) slurry of proteino id (crude

or fractionated) in distilled water or artificialseawater was heated to boiling for 30 sec. The

hot, yellow-brown supernatant was separatedfro m undissol ved ta rry solids. On Cooling toroom temperature, the solution deposited mi-crospheres. Morphological and colloidal stabil-ity of microspheres to titr atio n with dilute HC1or NaOH was moni tore d by optical micro scopy(Leitz Ortholux); a Radiometer pH meter

1 Reaction at 80 C for 12 days yielded smallamounts of proteinoid.


3/8

224

( M o d e l P H M 4 c ) w a s u se d t o m e a s u re p H o fm i c r o s p h e r e s u s p e n s i o n s.

1 . 2 .5 . G e l l s o e l e c t r i c F o c u s i n gT h e a p p a r a t u s c o n s i s t e d o f a B i o - R a d M o d e l

2 0 0 e l e c t r o p h o r e s i s s y s t e m a n d a B e c k m a nS p i n c o R P - 2 p o w e r s u p p l y. G e ls w e r e f o r m e di n 5 1 2 5 m m g la ss t u b e s t r e a t e d w i t h d im e -t h y l d i c h l o r o s i l a n e b e f o r e u s e . T h e f o l l o w i n gs t o c k s o l u t i o n s w e r e m a d e f r o m d i st il l ed w a t e rs a t u r a t e d w i t h n i t r o g e n ( S m i t h , 1 9 6 8 ) :

( A ) M o n o m e r s t o c k s o l u t i o n : 1 4 g a c r y l-a m i d e a n d 0 . 3 6 7 5 g B I S / 5 0 m l s o l u t i o n

( B ) I n i t ia t o r s t o c k s o l u t i o n : 0 . 0 7 g a m m o -

n i u m p e r s u l f a t e / 5 0 m l s o l u t i o n .G e l s w e r e p r e p a r e d b y r a p i d l y m i x i n g 5 m l ( A ) ,5 m l w a t e r , 0 . 1 m l T E M E D , 1 m l a m p h o l y t es o l u t i o n a n d 1 0 m l ( B ) , t h e n f i l li n g e a c h g la s st u b e . G e l a t i o n o c c u r r e d a f t e r 5 m i n ; t h e l e n gt ho f t h e g e l b e d w a s 11 5 m m . G e l t u b e s w e r ei n s ta l le d i n t h e a p p a r a t u s a n d t h e t o p o f e a c hb e d w a s l a y e r e d w i t h 0 .1 m l o f a 4 0 % s u c r o s es o l u ti o n . T h e c a t h o d e c o m p a r t m e n t { t op ) w a sf il le d w i t h 2 . 9 % d i e t h a n o l a m i n e a n d t h e a n o d ec o m p a r t m e n t w i t h 1 % H 2 S O 4 ( We l l n er , 1 9 7 1 ) .

S a m p l e s o l u t i o n s w e r e p r e p a r e d c o n t a i n i n g4 0 m g / m l o f e a c h p r o t e i n o i d o r f ra c t i o n i n a1 M u r e a s o l u t i o n c o n t a i n i n g 2 % a m p h o l y t e s .F i v e l a m b d a s o f t h is s o l u t i o n w a s la y e r e d o n ag e l b e d u n d e r t h e s u c r o s e s o l u t i o n .

E l e c t r o f o c u s i n g w a s c a r ri e d o u t a t 1 2 0 V f o r5 - - 1 0 h r . P r o t e i n o i d c o m p o n e n t b a n d s w e r el o c a t e d i n t h e g e ls b y t h e i r s t r o n g f l u o r e s c e n c eu n d e r 2 5 4 n m i r ra d i a t io n .

I . 2 . 6 . M i sce l l an eousA m i n o a c id c o m p o s i t i o n o f u n h y d r o l y z e d

a n d a c id h y d r o l y z e d p r o t e i n o i d f r a c ti o n s w e r ed e t e r m i n e d b y e s t ab l i sh e d m e t h o d s ( F o x e t a l. ,1 9 6 3 ) . M o l e c u l a r w e i g h t d i s t r i b u t i o n s w e r ee s t i m a t e d f r o m : g e l p e r m e a t i o n c h r o m a t o g -r a p h y o n B i o - G e l P - 1 0 ( 0 .5 % s o d i u m d o d e c y ls u l f a t e a s e l u e n t ; F i s h , 1 9 7 1 ) a n d S e p h a d e xL H - 2 0 ( m e t h a n o l a s e l u e n t ) ; d ia l y si s w i t h S p e c -t r a p o r 3 m e m b r a n e t u b i n g o f 3 5 0 0 m . w. c u to f f , a n d u l t r a f i lt r a t i o n w i t h B i o - R a d h o l l o wf i b re d e v i c es . A s h c o n t e n t o f f r a c t i o n 2 w a sd e t e r m i n e d a f t e r i g n it io n t o c o n s t a n t w e i g h t

b e l o w 9 0 0 C . T h e e x t e n t o f a m i n o a c i d ra c e m i -z a t io n w a s m e a s u r e d b y O R D o n 0 . 0 5 - - 0 .4 %f i lt e r e d a q u e o u s s o l u t i o n s w i t h a J A S C O

O R D / U V - 5 s p e c t r o p h o t o m e t e r . E s ta b li sh e dp r o c e d u r e s w e r e u s e d f o r t h e b i u r e t t e s t (C l a r k ,1 9 6 4 ) a n d t h e G r a m s t ai n ( F o x a n d Yu y a m a ,1 9 6 3 ) .

2 . R e s u l t s

T h e f o u r f r a c ti o n s o f s e a w a t e r p r o t e i n o i do b t a i n e d a r e l is t ed i n Ta b l e 1 , w i t h th e p r o p e r -t i e s s t u d i e d . F r a c t i o n 2 w a s s t u d i e d i n g r e a t e s td e t a i l b e c a u s e o f i ts o u t s t a n d i n g t e n d e n c y t o

y i e l d a d e n s e p o p u l a t i o n o f m i c r o s p h e r e s a t ah i g h p H .Ta b l e 2 c o m p a r e s f r a c t i o n 2 o f s e a w a t e r

p r o t e i n o i d a n d a si m i la r f r a c t i o n o f n e u t r a lp r o t e i n o id . T h e a m i n o a c i d c o m p o s i t i o n s f o rt h e t w o p r o t e i n o i d s a re c o m p a r a b l e e x c e p t f o rt h e h i g h e r c o n t e n t o f t y r o s i n e i n t h e s e a w a t e rp o l y m e r .

A l t h o u g h m o s t p r o p e r t i e s o b s e r v e d {Ta-b l e 3 ) a r e c o m m o n t o a l l t h e r m a l p r o t e i n o i d s( F o x a n d D o s e , 1 9 7 2 ) , a n e w c h a r a c t e r is t i ce m e r g e d o n e x a m i n a t i o n o f th e m i c r o s p h e r ep r e p a r a t i o n s .

T h e s e a w a t e r p r o t e i n o i d m i c r o s p h e r e s be g int o f o r m u p o n s li g ht c o o l i n g o f a h o t s o l u t i o n .T h e m o s t s i g n i fi c a n t f e a t u r e o f t h e s e u n i ts( F i g . 1 ) is t h e i r s t a b i l i t y a t h ig h p H . A s s t a t e de a r l i e r , m i x e d m i c r o s p h e r e s a r e s t a b l e a b o v ep H 7. T h i s f a c t s u g g e st e d t h a t t h e p r o t e i n o i dc o n t a i n s b o t h a c i di c a n d b a s ic c o m p o n e n t s . G e li s o e l e c t r i c f o c u s i n g v e r i f i e d t h i s i n f e r e n c e . A ss h o w n i n F i g . 2 , a c i d i c a n d b a s i c p r o t e i n o i d sc o n t a i n f a m il ie s o f c o m p o n e n t s w i t h p H va lu e s

e n t i r e l y i n t h e a c i d i c a n d b a s i c r e g i o n s o f t h e i rg e ls r e s p e c t i v e l y. S e a w a t e r p r o t e i n o i d , a s t h u so b s e r v e d , c o n t a i n s b o t h a c i d i c a n d b a si c p o l y -a m i n o a c i ds , e a c h o f li m i t e d h e t e r o g e n e i t y.

T h e m o b i l i t y p r e v i o u s l y o b s e r v e d i n a c i d i cp r o t e i n o i d m i c r o s p h e r e s is f o u n d t o e x i s t i ng r e a t e r d e g r e e i n t h o s e d e s c r i b e d h e r e . B r o w -n ia n m o t i o n h a s b e e n o b s e r v e d c o n t i n u o u s l yf o r as m u c h a s t e n d a y s , d u r i n g w h i c h f r a c t i o n 2s p h e r e s s e t t l e d o u t o n l y g r a d u a l l y o n g la sss u r f a c e s .


4/8

T A B L E 1

P r o p e r t i es o f f r a c t i o n s o f s e a w a t e r p r o t e i n o i d .

2 2 5

F r a c t i o n C o m p o s i t i o n W t F r e e P r o t e i n o i d a M o i s t u r e b M o l e c u l a rb y S o u r c e ( g) A m i n o S o l i d ( w t % ( w t % ) We i g h t R a n g e o f

A c i d s / o f s o l id ) M a j o r C o m p o n e n tS o l i d( w t % ) c

p H o f S u s -p e n s i o n o fM i c r o s p h e r e s

1 D i f f u s a t e s 7 . 6 2 0 . 9 4 2 . 0 1 6 . 3 < 3 , 0 0 0 7 . 91 + 2

2 D i f f u s a t e s 1 .3 1 9 . 2 1 8 .6 9 . 2 3 , 0 0 0 - - 1 0 , 0 0 0 9 .13 - - 7

3 D i s s o l v e d 0 . 1 8 . 4 1 9 . 2 - - > l 0 , 0 0 0 - -r e t e n t a t e

4 U n d i s s o l v e d 0 . 4 t r a c e 1 4 . 6 1 2 . 1 l 0 , 0 0 0 7 . 5s o l i d s

a We i g h t % h y d r o l y z a b l e t o a m i n o a c i d s ; f r a c t i o n 1 , i n a d d i t i o n t o s a l ts , p r o b a b l y c o n t a i n s l a r g e p r o p o r t i o n s o fd i k e t o p i p e r a z i n e s .b We i g h t l o ss a f t e r 413 h r a t 11 0 C o v e r P 2 0 5 ( 0 .1 m m H g ) .c F r o m a n a l y si s o f u : l h y d r o l y z e d p r o d u c t .

T A B L E 2

A m i n o a c i d c o m p o s i t i o n o f s e a w a t e r p r o t e i n o i d a n dn e u t r a l p r o t e i n o i d .

A m i n o a c id S e a w a t e r N e u t r a l

Ly s 5 . 0 8 . 4His 4 .1 3 .3A rg 5 . 0 3 . 4A s p 2 . 4 4 . 6T h r 1 . 6 0 . 3S e r 0 . 2 0 . 2G l u 1 4 . 8 1 0 . 3P r o 3 . 6 2 . 7G l y 8 . 3 8 . 3A l a 1 2 . 4 1 2 . 2C y s / 2 2 .1 5 . 2Va l 3 . 4 9 . 7M e t 6 . 5 6 . 8I l e u 2 . 4 4 . 7L e u 3 . 9 6 . 0Ty r : t 5 . 3 5 . 1P h e 6 . 9 4 . 6E x p r e s s e d a s m o l e % I N H 3 o m i t t e d f r o m t h e c a lc u l a-t i o n s ) .

T A B L E 3

C h a r a c t e r i s t i c s o f f r a c t i o n 2 ( Ta b l e 1 ) .

P r o t e i n o i d :1) 12% ash2 ) C o m p l e t e r a c e m i z a t io n ( O R D )3 ) P o s i t i v e b i u r e t t e s t4 ) L i m i t e d h e t e r o g e n e i t y5 ) C o m p o s i t i o n s i m i la r t o t h a t o f p r o t e i n6 ) M o l e c u l a r w e i g h ts o f m a n y t h o u s a n d

7 ) R e c o v e r a b i l i t y o f a m i n o a c i d s o n h y d r o l y s i s8 ) Te n d e n c y t o a g g r e g a t e t o c e l l -l i k e s t r u c t u r e s

M i c r o s p h e r e s :1 ) M i c r o s c o p i c s i z e r a n g e ( < 3 p )2 ) S t a b i l i t y f r o m p H 8 . 7 - - 9 . 9 w h e n f r e s h l y p r e p a r e d3 ) S t a b i l i t y f r o m p H 4 . 7 - - 9 . 5 o n a g i n g 1 0 d a y s4 ) P o s i t i v e G r a m s t a i n5 ) U n i f o r m i t y o f si z e6 ) N u m e r o u s n e s s7 ) A s s o c i a ti v e p a t t e rn s , i n c l u d i n g f o r m a t i o n o f ju n c -

t i o n s8 ) A b i l i t y t o b u d


5/8

2 2 6

i

+ - ~ . . ~ ,~ , - % . ' ~ " .

L

. i

15

F i g. 1 . S e a w a t e r p r o t e i n o i d m i c r o s p h e r e s. A ) A p p r o x i m a t e l y 1 p m i n d ia m e t e r. A m o r e c o n c e n t r a t e d s l u r r y y i e l d sla rg er s p h e r u l e s , B a n d C , e . g . , 1 2 0 m g / m l y i e l d s 2 . 5 p m s p h e r u l e s , m a n y w i t h b u d s , C .


6/8

Fig. 2. Gel isoelectric focusing of proteinoids at 25C.Seven percent crosslinked acrylamide gels, 5 mm x

115 ram; cathode (top) contained 2.9% ethanol-amine, anode contained 1% H2SO4; 120 V/5 hr, A:acidic proteinoid, B: seawater proteinoid, C: basicproteinoid. Solid areas represent well defined bands;cross-hatched areas are diffuse.

3. Discussion

The composition of thermal proteinoids hasbeen shown to be precisely, althoug h not neces-sarily linearly, re:ated to the pro port ions ofamino acids in the reac tion mixtur e (Fox et al.,1963; Fox and Waehneldt, 1968) from whichthey are prepared. By varying these propor-tions, one can l=roduce an almost limitlessvariety of proteinoids, each of remarkablylimited heterogeneity. With possible co-reac-tants ("prosthetic groups" in some cases) thereis theoretically encompassed most or all or-ganic and inorgaric compounds that,partici-pated in protobiological evolution. As a minorexample, inorganic phosphates or polyphos-

phates affect the composition and yield ofproteinoids (Fox, 1968). Dose and Rauchfuss{1972) have reporLed the prod ucti on o f acidicand basic pr oteinoids in a single preparation byheating an amino acid mixture with sodiumpolyphosphate.

The principal effect of seawater salt on thecomposition of proteinoid is in the tyrosinecont ent. The saline matrix appar ently increasesthe relative inco rporab ility, and perhaps stabil-ity, of the tyrosme. The known ability of

227

tyrosine to form magnesium complexes(Greenstein and Winitz, 1961) and the highcontent of tyrosine in this polymer may be a

significant contribu tion to the ash con tent offraction 2. The fact that the proteinoid formsin the presence of seawater salts extends theknowledge of the ruggedness of this polycon-densatio n, as earlier described for oth er geolog-ical materials such as basalt (F ox, 1965).

The stability of seawater proteinoid micro-spheres at high pH is explained by the fact thatit contains both acidic and basic componentsanalogous to mixed acidic plus basic micro-sphere systems. In such systems, inte ractions of

a basic macromolecule with an acidic onewould give a complex, less soluble than eithercomponent. Thus the simple, two-step con-ceptual sequence: amino acids -* preprotein -~protocell is modified by these experiments.The presence of seawater salts provides a routeto base-stable microspheres of mixed protein-oids and obviates the need for independentsyntheses of acidic and basic proteino ids on theprimitive Earth.

Aside fr om a possible very early period of anacidic ocean on the early Earth (Rube y, 1964),the p rimitive ocean is generally believed to havebeen at about pH 7.3-8.1. The seawater pro-teinoid is thus of interest as one model for theorigin of protocells in such an ocean. Moreover,the origin of cellular polyme riza tions yieldingproteins and nucleic acids can be th oug ht of asfavored by high pH as they are in con tem por ar ycells (Kirsch et al., 1960; Aposhian and Korn-berg, 1 962). Buddi ng {Fig. 1B) has been shownto function as a necessary step in a primordialreproductive cycle involving separation of the

buds (cf. Lehninger, 1970) by mechanicalshock or thermal tre atmen t (Fox et al., 1967).Those units that ha ppened to have prolongedmobili ty would acc ordingly have had enhancedopportunity for mechanical separation or fortravel into warmer waters, which could causeseparation followed by accretive growth. Sea-water proteino id microspheres would thus havebeen relatively highly adapted to reproductiveevents. For instance, a model protoribosomecapable of making peptides from phenylalanine


7/8

228

a n d AT P ( F o x e t a l ., 1 9 7 4 ) h a s a s a n e c e s s a r yc o m p o n e n t a b a s i c p r o t e i n o i d .

Va p o r i z a t i o n o f w a t e r f r o m a p r i m i t iv e

l a g o o n a n d e x p o s u r e o f t h e r e s u l ta n t e v a p o r i t ed e p o s i t o f i n o r g a n i c s a l ts a n d a m i n o a c i d s t ot e m p e r a t u r e o f 70 t o 2 0 0 C p r o v i d e a s i m p l ep r o c e s s t h a t c o u l d h a v e o c c u r r e d o n p e ri v o l -c a n i c a n d o t h e r r e g i o n s o f t h e E a r t h ' s s u r f a c e( F o x , 1 9 6 4 ) . T h e m o d e l a n d c o n c e p t a res t r e n g t h e n e d b y t h e f i nd i n g t h a t s e a w a t e r p r o -t e i n o i d y i e l d s c e l l - li k e s t r u c t u r e s t h a t a r e s t a b l ei n a n a l k a l i n e o c e a n . R o h l f i n g ' s b a s i c m i c r o -s p h e r e s ( 1 9 7 5 ) p r o v i d e a n a l t e r n a t i v e e x p l a n a -t io n w i t h a m i c r o u n i t o f o t h e r p r o p e r t ie s . T h e

f a c t th a t s p h e r u le s o f s e a w a t e r p r o t e i n o i d a rer e l a t i v e l y s t a b l e a l s o i n w a r m w a t e r is c o n s is -t e n t w i t h t h e g e o l og i c a l m o d e l o f T u r c o t t e e ta l. ( 1 9 7 4 ) . T u r c o t t e e t a l. h a v e l i n k e d t h e f i r stc e l ls a l s o t o m i c r o f o s s i l s , a n d t o a g l o b a l t h e r -m a l e v e n t r e s u l t in g f r o m a M o o n - E a r t h i n te r a c -t io n . A l t h o u g h s u c h a n e v e n t w a s c o n c e p t u a l l yn o t n e c e s s a r y t o p r o d u c e t h e f ir s t p r o t e i n o i dm i c r o s p h e r e s , a g r a n d b u r s t o f p r o t o c e l l s c o u l dh a v e r e s u l t e d a t t h a t t i m e ( 3 b i l l i o n y e a r s a g o ) .

I n o t h e r s i m u l a t i o n s o f s e t t i n g s s u c h a s t h eo n e e x a m i n e d h e r e , s e a w a t e r s a l ts h a v e b e e ns h o w n t o i n c r e a s e t h e y i e ld s o f p u r i n e n u c l e o -s id e s f r o m r e a c t i o n s b e t w e e n p u r in e b a s e s a n dr i bo s e a t t e m p e r a t u r e s n e a r th e b o i l i n g p o i n t o fw a t e r , b u t i n t h e a b s e n c e o f w a t e r ( F u l l e r e t a l. ,1 9 7 2 ) . Q u e s t i o n s o f t e m p e r a t u r e , p r e s e n c e o ra b s e n c e o f w a t e r , s e q u e n c e o f e v e n t s , e t c . in th eg e n e r a l t h e o r y a s r a i se d b y o t h e r s , h a v e b e e nc r i t i c a l ly d i s c u s s e d i n tw o r e c e n t re v i e w s ( F o x ,1 9 7 3 b , 1 9 7 4 c ) .

S e a w a t e r p r o t e i n o i d , in th e c o n t e x t o f at h e r m a l m o d e l o f o ri g in s , p r o v i d e s e x p e r i m e n -

t a l s u p p o r t f o r t h e c o n c e p t t h a t l i f e c o u l d h a v ea r i s e n i n t h e s e a ( F o x e t a l. , 1 9 5 9 ) , a s e a r l i e rp r o m u l g a t e d b y O p a r i n ( 1 9 2 4 ) .

A c k n o w l e d g m e n t s

We t h a n k M r . C .R . W i n d s o r f o r a m i n o a c ida n a l y s is , D r . L . L . H s u f o r h e l p w i t h t h e G r a ms t a in , a n d M r . T. I w a s a k i fo r i n s t r u m e n t a l a i d .

T h e r e s e a rc h h a s b e e n s u p p o r t e d b y N A S A

G r a n t N G R 1 0 - 0 0 7 - 0 0 8 . C o n t r i b u t i o n n o . 2 7 8o f T h e I n s t i t u t e f o r M o l e c u l a r a n d C e l l u la rE v o l u t i o n .

R e f e r e n c e s

Aposh ian , H .V. and A. Kornberg , 1962 , Enzym at icsyn thes i s o f deoxyr ibonuc le ic ac id . IX . The Po ly -merase fo rm ed a f t e r T2 bac te r iophage in fec t ion o fE s c h e r i c h i a c o i l : a new enzyme, J . B io l . Chem.237, 519.

Cavanaugh , G .M. , ed . , 1956 , "Formulae and Methods ,V, o f the Mar ine B io log ica l La bora to ry Chemica lRoom" (Woods Hole , Mass . ) p . XX.

Cla rk , J .M. , ed . , 1964 , "Exper im en ta l B ioche mis t ry "(W.H. Freeman and Co. , San Francisco) , p . 95.

Dose , K . and H. Rauchfuss , 1972 , On the e l ec t ro -p h o r e t ic b e h a v i or o f t h e r m a l p o l y m e r s o f a m i n oacids , in : "Mole cular Evo lut ion: Prebiological andBiological ," eds . : D.L. Rohlf ing and A.I . Opar in(Plenum Press , New York) , p . 199.

F i sh, W.W . , 1971 , G e l ch rom atog raph y in dena tu r ingso lven t s , me thod fo r the s tudy o f p ro te in subun i tc o m p o s i t i o n , J . A gr. F o o d C h e m . 1 9 , 6 6 0 .

Fox , S .W. , 1965 , A theory o f macrom olecu la r andcel lular or igins , Nature 205, 328.

Fox , S .W. , 1968 , Na tu ra l po lym ers : ab io t i c po lymer i -za t ion and se l f -o rgan iza t ion , in : "Encyc loped ia o f

Po lymer Sc ience and Techno logy, " vo l . 9 , eds . :I t .F. Mark , N .G. Gay lo rd , and W .M. Bika les (In te r-sc ience, New York) , p . 284 .

Fox, S .W., 1973a, Molecular evolut ion to the f i rs tce l l s , Pure Appl . Chem. 34 ,641 .

Fox , S .W. , 1973b , Or ig in o f the ce l l: exper im en t s andpremises , Na tu rwissenschaf t en 60 ,359 .

Fox, S .W., 1974a, Origins of b iological informat ionand the genet ic code, Molec . Cel l . Biochem. 3 ,129.

Fox , S .W. , 1974b , The rm ody nam ic pe r spec t ives andthe or igin of l i fe , in : "Quantum Stat is t ica l Me-chanics in the Natu ral Sciences ," eds . B. Kursu-noglu, S .L. Mintz , and S.M. Widmayer (PlenumPress , New York) , p . 119.

Fox , S .W. , 1974c , The p ro te ino id theory o f the o r ig inof l i fe and compet ing ideas , Amer. Biol . Teacher36, 161.

Fox , S .W. and K . Dose , 1972 , "M olecu la r Evo lu t ionand the Or ig in o f L i fe" (W.H. F reema n and Co . ,San Franc i sco) .

Fox , S .W. and K. Harada , 1960 , The the rmal copo ly -m e r i z a t i o n o f a m i n o a c i d s c o m m o n t o p r o t e i n , J .Am. Chem. Soc . 82 , 3745 .

Fox , S .W . and T .V. Waehne ld t , 1968 , The the rmalsyn thes i s o f neu t ra l and bas ic p ro te ino ids , B io -c h i m . B i o p h ys . A c t a 1 6 0 , 2 4 6 .


8/8

F o x , S . W. a n d S . Yu y a m a , 1 9 6 3 , E f f e c t s o f t h e G r a ms t ai n o n m i c r o s p h e r e s fr o m t h e r m a l p o l y a m i n oa c i d s , J . B a c t e r i o l . 8 5 , 2 7 9 .

F o x , S . W. , K . H a r ac l a a n d J . K e n d r i c k , 1 9 5 9 , S y n t h e -s is o f m i c r o s c o p i c sp h e r e s i n se a w a t e r i n : " I n t e r -n a t i o n a l O c e a n o g r a p h i c C o n g r e s s , " p r e p r i n t s , e d . :M . S e a r s ( A m e r. A s s o c . A d v a n c e m e n t S c i . , Wa s h -i n g t o n ) , p . 8 0 .

F o x , S . W., K . H a r ac ! a, K . R . W o o d s a n d C . R . Wi n d s o r ,1 9 6 3 , A m i n o a c i d c o m p o s i t i o n s o f p r o t e in o i d s ,A r c h . B i o c h e m . i = ;i op h ys . 1 0 2 , 4 3 9 .

F o x , S . W. , R . J . M c C a u l e y a n d A . Wo o d , 1 9 6 7 , Am o d e l o f p r i m i :: iv e h e t e r o t r o p h i c p r o l i f e r a t i o n ,C o m p . B i o c h e m . P h y s io l . 2 0 , 7 7 3 .

F o x , S .W . , C . -T. Wa n g , T.V. Wa e h ne ld t , T. Na kash i -m a , G . K r a m p i t z , T. H a y a k a w a a n d K . H a r a d a ,1 9 7 0 , M e t h o d s f o r p r o d u c i n g o c t a d e c a t o n i c a n h y -

d r o p o l y m e r s o f a m i n o a c i d s , i n : " P e p t i d e s : C h e m -i s t r y a n d B i o c h e m i s t r y, " e d s. B . We i n s t e i n a n d S .L a n d e ( M a r c e l D e k k e r , I n c . , N e w Yo r k ) , p . 4 9 9 .

F o x , S . W. , J . R . J u n g c k a n d T. N a k a s h i m a , 1 9 7 4 ,F r o m p r o t e in o i d m i c ro s p h e re to c o n t e m p o r a r yc e ll : f o r m a t i o n o f i n t e r n u c l e o t i d e a n d p e p t i d eb o n d s b y p r o t e i r t o i d p a r t i c l e s, O r i g i n s o f L i f e 5,2 2 7 .

F u l l e r , W. D . , R . A . S a n c h e z a n d L . E . O rg e l , 1 9 7 2 ,S t u d i e s i n p r e b i o t i c s y n t h e s i s . V I . S y n t h e s i s o fpu r ine nucleos ide~; , J . M ol . Bio l . 67 , 25 .

G r e e n s t e i n , J . P. a n d M . Wi n i t z , 1 9 6 1 , " C h e m i s t r y o ft h e A m i n o A c i d :; " ( J o h n W i le y a n d S o n s , N e wYo r k ) , p . 6 1 8 .

H a r a d a , K . a n d S . W. F o x , 1 9 6 5 , T h e r m a l p o l y c o n d e n -s a t i o n o f f r e e a n a in o a c id s w i t h p o l y p h o s p h o r i cac id , i n : "T he O r il,~ in s o f P r e b i ~ log i ca l Sy s t e m s ando f t h e i r M o l e c u l a r M a t r i c e s , " e d . S . W. F o x ( A c a -d e m i c P r es s , N e w Yo r k ) , p . 2 8 9 .

I -I su , L . L . , 1 9 7 4 , P r o t e i n o i d m i c r o s p h e r e s a s m o d e l sf o r p r i m o r d i a l o rg a n i c e v o l v i n g s y s t e m s , P h . D . d i s -s e r t a t i o n , U n i v e r s i t y o f M i a m i .

Hsu , L .L . , S . B rook ,. ' a nd S . W. Fo x , 19 7 1 , C on jug a -t i o n o f p r o t e i n o i d m i c r o s p h e r e s : a m o d e l o f p r i-

229

m o r d i a l c o m m u n i c a t i o n , C u r r e n t s M o d . B i o l . 4 ,12 .

K i r s c h , J . F. , P. S i e k e v i t z a n d G . E . P a l a d e , 1 9 6 0 ,A m i n o a c i d i n c o r p o r a t i o n i n v i t ro b y r ib o n u c l e o -p r o t e i n p a r t i c l e s d e t a c h e d f r o m g u i n e a p i g l iv e rm i e r o s o m e s , J . B io l . C h e m . 2 3 5 , 1 4 1 9 .

L e h n i n ge r , A . L . , 1 9 7 0 , " B i o c h e m i s t r y " ( W o r t h a ndC o . , N e w Yo r k ) .

O p a r i n , A . I. , 1 92 4 , " P r o i s k h o z d e n i e Z h i z n y " ( I zdM o s k o v s h i i R a b o e h i i , M o s c o w ) .

R o h l f i n g , D . L . , 1 9 7 5 , C o a c e r v a t e - l i k e m i c r o s p h e r e sf r o m l y s i n e - r ic h p r o t e i n o i d , O r i g in s o f L i f e 6 , 2 0 3 .

R o h l f i n g , D . L . a n d S . W. F o x , 1 9 6 9 , C a t a l y t i c a c t iv -i ti es o f t h e r m a l p o l y a n h y d r o - a - a m i n o a c id s , A d -v a n c e s C a t a l . 2 0 , 3 7 3 .

R u h e y, W. W. , 1 9 6 4 , G e o l o g i c h i s t o r y o f s e a w a t e r , i n :" T h e O r i gi n a n d E v o l u t i o n o f A t m o s p h e r e s a n d

O c e a n s , " e d s .: P. J . B r a n c a z io a n d A . G . W. C a m e r o n( J o h n Wi l e y a n d S o n s , N e w Y o r k ) , p . 1 .S a u n d e r s , M . A . a n d D . L . R o h l f i n g , 1 9 7 2 , P o l y a m i n o

a c id s : p r e p a r a t i o n f r o m r e p o r t e d p r o p o r t i o n s o f" p r e b i o t i c " a n d e x t r a t e r r e s t r i a l a m i n o a c i d s , S c i -ence 176 , 172 .

S m i t h , I ., 1 9 6 8 , " C h r o m a t o g r a p h i c a n d E l e c t r o p h o -r e t i c Te c h n i q u e s , " v o l . I I , 2 n d e d . ( I n t e r s c i e n c e ,N e w Yo r k ) , p . 3 6 5 .

S n y d e r , W. D . a n d S . W. F o x , 1 9 7 3 , A s s e m b l y o f m i -c r o s p h e r e s f r o m p r o t e i n o i d s y n t h e s i z e d i n p r e s-e n c e o f s e a w a t e r sa l t s, F e d e r a t i o n P r o c . 3 2 , 6 4 0abs .

Tu r c o t t e , D . L . , J . C . N o r d m a n n , a n d J . L . C i s n e , 1 9 7 4 ,E v o l u t i o n o f t h e M o o n ' s o r b i t a n d t h e o r i g i n o fl i f e , Na tu r e 251 , 124 .

We l lne r, D . , 1971 , E l ee t ro fo cus in g i n ge l s , Ana l .C h e m . 4 3 , 5 9 A .

Yo u n g , R . S ., 1 9 6 5 , M o r p h o l o g y a n d c h e m i s t r y o fm i c r o s p h e r e s f r o m p r o t e i n o i d , i n : " T h e O r ig i n s o fP r e b i o l o g i c a l S y s t e m s a n d o f t h e i r M o l e c u l a r M a -t r i c e s , " e d . : S . W. F o x ( A c a d e m i c P r e s s, N e wYo r k ) , p . 3 4 7 .

1975 a model for the origin of stable protocells in a primitive alkaline ocean

Documents