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Age and Paleogeographical Origin of Dominican Amber Author(s): Manuel A. Iturralde-Vinent and R. D. E. MacPhee Reviewed work(s): Source: Science, New Series, Vol. 273, No. 5283 (Sep. 27, 1996), pp. 1850-1852 Published by: American Association for the Advancement of Science Stable URL: http://www.jstor.org/stable/2891099 . Accessed: 08/06/2012 10:47 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected].

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by each Cu withinthe [Cu302]core. Upon inspectionof the crystalstructureof the fully reducedformof ascorbateoxidase(11), the threetrigonally ligatedCu(I)centers(average Cu Cu distance,4.5 A) appeargeometrically predisposed towardaccommodation of ?2 and

16.

17.

formation of a [Cu302I cluster. However, no

currentspectroscopic studiesof the metastable oxygenintermediates of multicopper oxidases and their derivativessupportthe existence of an intenselyabsorbingoxo-Cu(III)chromophore,andno unusuallyshortCu-Obond distancessuch as those observedin 2 are indicated(12, 13, 32). In accordancewith these studies,however, the facile reaction of three Cu(I) monomerswith 02 to form 18.

the mixed-valence bis(R.3-oxo)[Cu(lI)Cu(II)

Cu(III)]species2 does suggestthat 02 bond cleavageat trinuclearCu sites requiresfull 4e- reductionof 02. In the case of native laccase,the fourthelectronis providedby the remote"blue"Cu center,whereasin 2, the extraelectronmustbe obtainedat the cost of furtheroxidationof one of the Cu sites.

19. 20.

REFERENCESAND NOTES 1. K. D. Karlinand Z. Tyeklar,Eds., BioinorganicChemistry of Copper (Chapman & Hall,New York, 1993). 2. N. Kitajimaand Y. Moro-oka, Chem. Rev. 94, 737 (1994). 3. E. 1.Solomon, M. J. Baldwin, M. D. Lowery, ibid. 92, 521 (1992); E. I.Solomon and M. D. Lowery,Science 259,1575 (1993). 4. K. D. Karlinand S. Fox, inActive Oxygen in Biochemistry, J. S. Valentine, C. S. Foote, A. Greenberg, J. F. Liebman, Eds. (Chapman & Hall, Glasgow, 1995), vol. 3, pp. 188-231. 5. K. Fujisawa, M. Tanaka, Y. Moro-oka, N. Kitajima,J. Am. Chem. Soc. 116, 12079 (1994); M. Harata, K. Jitsukawa, H. Masuda, H. Einaga, ibid., p. 10817. 6. K. A. Magnus, H. Ton-That, J. E. Carpenter, Chem. Rev. 94, 727 (1994). 7. T. N. Sorrell, W. E. Allen, P. S. White, Inorg. Chem. 34, 952 (1995); W. E. Lynch, D. M. Kurtz, S. K. Wang, R. A. Scott, J. Am. Chem. Soc. 116,11030 (1994); S. Mahapatra,J. A. Halfen, E. C. Wilkinson,L. Que, W. B. Tolman, ibid., p. 9785. 8. D. J. Spira-Solomon, M. D. Allendorf,E. I. Solomon, J. Am. Chem. Soc. 108, 5318 (1986). 9. A. Messerschmidt et al., J. Mol. Biol. 224, 179 (1992). 10. M. D. Allendorf,D. J. Spira, E. I.Solomon, Proc. Natl. Acad. Sci. U.S.A. 82, 3063 (1985); L. Ryden and 1. Bjbrk,Biochemistry 15, 3411 (1976); I. Zaitseva et al., J. Biol. Inorg. Chem. 1, 15 (1996). 11. A. Messerschmidt, H. Luecke, R. Huber,J. Mol. Biol. 230, 997 (1993). 12. J. L. Cole, P. A. Clark, E. I. Solomon, J. Am. Chem. Soc. 112, 9534 (1990). 13. J. L. Cole, G. 0. Tan, E. K. Yang, K. 0. Hodgson, E. I. Solomon, ibid., p. 2243. 14. The (1R,2R)-cyclohexanediamine backbone was chosen both for its preorganized nature and its chirality. In its energetically preferred conformation with the two amine substituents equatorially positioned, this ligand is preorganized for binding a single metal. The enantiomeric purityof the ligand significantly reduces the probabilityof forming diastereomeric complexes. 15. Although1 has not been structurallycharacterized, its 1H NMR spectrum in the diamine ligand region is nearlyidenticalto that of the structurallycharacterized trigonalplanar complex [LCu(PPh3)](CF3S03), which is formed upon additionof PPh3 to a solution of 1. The N-perethylated analog of 1, [(L')Cu(CH3CN)](CF3S03) [L' = N,N,N',N'-tetraethyl-trans-(1R,2R)-cyclohex-

1850

21.

anediamine],with bound CH3CNhas also been structurallycharacterized as a trigonalplanarspecies (18). Reported concentrations and molar absorptivites are uncorrected for the thermal contraction of CH2CI2at below-ambient temperatures, consistent with other reports. The product of oxygenation depends on the concentrationof 1. Reaction of solutions at or below 1 mM in 1 generates a different species X with extremely intense electronic and vibrationaltransitions [per Cu atom: molar absorptivity ? = 10,000 M-1 cm-1 at wavelength Xmax = 295 nm, s = 13,000 M-1 cm-1 at 392 nm; resonance Raman features at 607 and 583 cm-1 for 1602- and 1802-derived samples, respectively (CH2CI2solution, 407-nm excitation)].The close spectroscopic resemblance of X to the structurally characterized dimer [(Bn3TACN)2Cu202](SbF6)2recently reported [J. A. Halfenet al., Science 271, 1397 (1996)] suggests that it is a similar 2:1 Cu:02 complex (Bn3TACN= 1,4,7-tribenzyl-1,4,7triazacyclononane). Supporting informationis availablefrom the author or at the Science Web site http://www.sciencemag. org/ science/feature/beyond/#cole. Includedare synthetic procedures and spectroscopic characterizationdata for all new compounds and x-ray structuralinformation, includingtables of crystal collection data, positional and thermal parameters, and interatomic distances and angles. Isolated yield, 60%. The x-ray crystal data is available (18). Crystal data for [2]-4CH2CI2:brown rhombic blocks from cold (-40?C) CH2C2-ether; monoclinic C2 (no. 5), a = 28.0300(1) A, b = 16.8004(3) A, c = 15.3760(2) A, ) = 119.158(1)?, V= 6323.2(1) A3, and Z = 4; 14,745 reflections were collected and appropriately averaged (18), 9779 of which were unique (150 K, 30 < 20 < 460); 7124 reflections [I Fo I>4o(Fj)] yield R = 7.4 and Rw = 7.6. Although the two clusters are crystallographically unique, they are isostructural to within a rootmean-square (rms) deviation of 0.162 A (0.093 A

rms for the N6Cu3O2 core). 22. The structure of 2 bears a strong superficialresemblance to that of a previously reported macrocyclic species; however,this therbis(,.3-hydroxo)tricopper(ll) mallystable clusterexhibitsfullthreefoldsymmetry,has normalCu(ll)-Oand Cu(ll)-Ndistances, and carries an overall charge of 4+ [J. Comarmond, B. Dietrich,J. Lehn, R. Louis,Chem. Commun.1985, 74 (1985)]. 23. K. Hesterman and R. Hoppe, Z. Anorg. Allg. Chem. 367, 249 (1969). 24. Formulationof 2 as a p,3-hydroxo-pL3-oxotricopper(Il) species would also be consistent with an overall charge of 3+ but fails to rationalizethe short Cu-O bonds exhibited by the unique Cu site. 25. D. F. Evans, J. Chem. Soc. 1959, 2003 (1959). 26. P. N. Schatz, R. L. Mowery, E. R. Krausz,Mol. Phys. 35,1537 (1978). 27. Ferromagnetic interactions in Cu202 cores have been reported previously[forexample, P. Chaudhuri et al., Angew. Chem. lnt. Ed. Engl. 24, 57 (1985)]. 28. M. J. Baldwinet al., J. Am. Chem. Soc. 114,10421 (1992). 29. M. P. Youngblood and D. W. Margerum, Inorg. Chem. 19, 3068 (1980). 30. D. Chang, T. Malinski,A. Ulman, K. Kadish,ibid. 23, 817 (1984). 31. C. LeVanda, K. Bechgaard, D. 0. Cowan, M. D. Rausch, J. Am. Chem. Soc. 99, 2964 (1977). 32. W. Shin et al., J. Am. Chem. Soc. 118, 3202 (1996); P. A. Clarkand E. I.Solomon, ibid. 114, 1108 (1992). 33. We thank the University of California Mass Spectrometry Facility (Department of Pharmaceutical Chemistry, San Francisco); Z. Hou and V. Mahadevan for experimental assistance; and F. Hollander for use of the Siemens SMART diffractometer at the University of California at Berkeley. Funding provided by NIH grants GM50730 (T.D.P.S.) and DK31450 (E.l.S.) and an NSF predoctoral fellowship (A.P.C.). 22 April 1996; accepted 5 August 1996

Age and Paleogeographical Origin of Dominican Amber and R. D. E. MacPhee ManuelA. Iturralde-Vinent* The age and depositional history of Dominican amber-bearing deposits have not been well constrained. Resinites of different ages exist in Hispaniola, but all of the main amberiferous deposits in the Dominican Republic (including those famous for yielding biological inclusions) were formed in a single sedimentary basin during the late Early Miocene through early Middle Miocene (15 to 20 millionyears ago), according to available biostratigraphic and paleogeographic data. There is little evidence for extensive reworking or redeposition, in either time or space. The brevity of the depositional interval (less than 5 million years) provides a temporal benchmark that can be used to calibrate rates of molecular evolution in amber taxa.

In the DominicanRepublic,amber(1) occursin commerciallyexploitablequantities in two zones (Fig. 1): north of Santiagode los Caballeros(the "northernarea") and northeastof Santo Domingo (the "eastern M. A. Iturralde-Vinent,Museo Nacional de HistoriaNatural, Obispo 51, La Habana CH 10100, Cuba. R. D. E. MacPhee, Department of Mammalogy, American Museum of NaturalHistory,New York, NY 10024-5192, USA. *To whom correspondence should be addressed. Present address: Department of Mammalogy, American Museum of NaturalHistory,New York, NY 10024-5192, USA. E-mail:[email protected]

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area"). Amber from the northern area has been suggested to be as old as Early Eocene or as young as Early Miocene (2-7); estimates for the eastern area are more diverse, ranging from Cretaceous to Recent (2-4, 6-9). Age spreads of this magnitude are implausible, but to date no resolution of the age of Dominican amber has met with wide acceptance. The resolution offered here is based on a synthesis of available biostratigraphic and paleogeographic data from several parts of Hispaniola (Fig. 2). In the eastern area, amber-bearingsedi-

ao ments occur in the - 100-m-thickYanigua sentingripplemarks. Amberfragmentsfrom Formation(Fm),composedof organically rich these sandsshow few surfacesignsof translaminatedsand,sandyclay,andsomeinterca- port and can reach lengthsof 30 to 40 cm. lated lignite layersup to 1.5 m thick. Plant Ligniteoccursin the formof thin lamellae debrisis foundat low frequencythroughout. within the sandstones;carbonizedwood Isolatedbedsof graveland calcareniteoccur, fragmentsare also common. These rocks but truealluvialsedimentsareabsent.Amber gradeinto flyschoid,deeperwaterdeposits pieces are found embeddedin lignite and containingdetritalamber(17) underlainby sandyclay.In additionto indicativesedimen- thick conglomerate(14, 16). Microfossils taryfeatures,the characterof the invertebrate (18) in the amber-bearingunit correlate and vertebratefossilsfromthese beds (thin- with faunalzones of Earlyto MiddleMioshelledmollusks,foraminifera, andostracods; cene age (5, 14-16). crocodiles,sirenians,and turtles)implythat Paleogeographically,the eastem and depositionoccurredin a near-shorecontext, northemareaswerepartof the samesedimenprobablyin coastallagoons(8, 10) fronting tarybasinthat was laterdisruptedby movelow, denselyforestedhills (11). Microfossil ments alongmajorfaults(Fig. 1). Paleocurassemblages(12) and zone definitions(13) rent analysis(19) of amber-bearing rocksof indicatea late Earlyto earlyMiddleMiocene the northemareaindicatesthat the sediment agefor this formation. sourcewas locatedtowardthe southeast,so In the northernarea,the amber-bearing the onlyplausiblesourceof resininputwould unit comprisesthe upper300 m of the La havebeenforestssurrounding the depositionToca Fm, a 1200-m-thick Oligocene to al basin (Fig. 1). In the eastemarea,slopeMiddleMiocene suite of clastic rocks(14- washcarriedresinitesinto nearbycoastalla16). The amberiferousunit is composedof goons, where they were apparentlyconcensandstone with occasional conglomerate tratedin lenslikepockets.Resinitesin the La that accumulatedin a deltaicto deep-water Toca Fm were probablyslope-washedinto environment. Individual beds-thick, riverchannelscuttingthe ancestralCordillera coarse, and tail-gradedor massiveat their Central,then transported with sandand silt base- grade into amber-containingsand- into the deltaicanddeep-water environments stone with parallellamination,rarelypre- of the basin.Hydrodynamic experiments(20) Altamira

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indicate that Hymenaearesin and copal float in fast-movingfresh water but sink when the current is slow or negligible. Freshresinfloats in saline water,but copal and ambermay float or sink dependingon the density of the individual specimen. Therefore,fresh resin and copal entering high-energy marine environments would probablyhave been widely dispersed. Outside the majormining areas,amber occursin smallquantitiesin turbiditicfacies of the Earlyto MiddleMioceneSombrerito Fm (21), south of the CordilleraCentralin the areaof PlateauCentral-SanJuan.Trace amountshave also been reportedfrom lagoonallignite-bearingsedimentsof the early Middle Miocene MaissadeFm in Haiti (22). These occurrencesrepresentan external temporal control for the age of the amber-bearing depositsnorthof the Cordillera Central(Figs. 1 and 2). In combination,these data indicatethat the amber-bearing depositsof the Dominican Republicare uniformlylate Earlyto early MiddleMiocenein age(15 to 20 millionyears ago).However,thisconclusiondoesnot agree with effortsto dateamberthroughthe use of visualized exomethyleneresonancesignatures by nuclearmagneticresonancespectroscopy (NMRS)(7). In orderto derivean ageassess-

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