Copper Binding to the Amyloid-β (Aβ) Peptide Associated with Alzheimer's Disease

There is now direct evidence that copper is bound to amyloid-β peptide (Aβ) in senile plaque of Alzheimer's disease. Copper is also linked with the neurotoxicity of Aβ and free radical damage, and Cu2+ chelators represent a possible therapy for Alzheimer's disease. We have therefore used a range of complementary spectroscopies to characterize the coordination of Cu2+ to Aβ in solution. The mode of copper binding is highly pH-dependent. EPR spectroscopy indicates that both coppers have axial, Type II coordination geometry, square-planar or square-pyramidal, with nitrogen and oxygen ligands. Circular dichroism studies indicate that copper chelation causes a structural transition of Aβ. Competition studies with glycine and l-histidine indicate that copper binds to Aβ-(1–28) at pH 7.4 with an affinity of Ka ∼107m–1. 1H NMR indicates that histidine residues are involved in Cu2+ coordination but that Tyr10 is not. Studies using analogues of Aβ-(1–28) in which each of the histidine residues have been replaced by alanine or in which the N terminus is acetylated suggest that the N terminus and His13 are crucial for Cu2+ binding and that His6 and His14 are also implicated. Evidence for the link between Alzheimer's disease and Cu2+ is growing, and our studies have made a significant contribution to understanding the mode of Cu2+ binding to Aβ in solution. There is now direct evidence that copper is bound to amyloid-β peptide (Aβ) in senile plaque of Alzheimer's disease. Copper is also linked with the neurotoxicity of Aβ and free radical damage, and Cu2+ chelators represent a possible therapy for Alzheimer's disease. We have therefore used a range of complementary spectroscopies to characterize the coordination of Cu2+ to Aβ in solution. The mode of copper binding is highly pH-dependent. EPR spectroscopy indicates that both coppers have axial, Type II coordination geometry, square-planar or square-pyramidal, with nitrogen and oxygen ligands. Circular dichroism studies indicate that copper chelation causes a structural transition of Aβ. Competition studies with glycine and l-histidine indicate that copper binds to Aβ-(1–28) at pH 7.4 with an affinity of Ka ∼107m–1. 1H NMR indicates that histidine residues are involved in Cu2+ coordination but that Tyr10 is not. Studies using analogues of Aβ-(1–28) in which each of the histidine residues have been replaced by alanine or in which the N terminus is acetylated suggest that the N terminus and His13 are crucial for Cu2+ binding and that His6 and His14 are also implicated. Evidence for the link between Alzheimer's disease and Cu2+ is growing, and our studies have made a significant contribution to understanding the mode of Cu2+ binding to Aβ in solution. Alzheimer's disease (AD) 1The abbreviations used are: AD, Alzheimer's disease; Aβ, amyloid-β peptide; EPR, electron paramagnetic resonance. 1The abbreviations used are: AD, Alzheimer's disease; Aβ, amyloid-β peptide; EPR, electron paramagnetic resonance. is characterized by innumerable deposits of extracellular amyloid plaques. A small peptide, amyloid-β peptide (Aβ), plays a critical role in the initial build up of these amyloid plaques and is the main constituent of the amyloid deposits (1Masters C.L. Simms G. Weinman N.A. Multhaup G. McDonald B.L. Beyreuther K. Proc. Natl. Acad. Sci. U. S. A. 1985; 82: 4245-4249Google Scholar, 2Kang J. Lemaire H.G. Unterbeck A. Salbaum J.M. Masters C.L. Grzeschik K.H. Multhaup G. Beyreuther K. Muller-Hill B. Nature. 1987; 325: 733-736Google Scholar). In addition, genetic alterations underlying familial AD are associated with an increase in the production and/or the deposition of Aβ in the brain (3Roses A.D. Curr. Opin. Neurobiol. 1996; 6: 644-650Google Scholar, 4Selkoe D.J. Science. 1997; 275: 630-631Google Scholar, 5Selkoe D.J. J. Biol. Chem. 1996; 271: 18295-18298Google Scholar, 6Mills J. Reiner P.B. J. Neurochem. 1999; 72: 443-460Google Scholar). Amyloid-β peptide can be between 39 and 43 residues in length, of which Aβ-(1–40) and Aβ-(1–42) are the most abundant fragments. The N-terminal portion of Aβ is hydrophilic, whereas the C terminus amino acids 29–42 are rich in hydrophobic residues and represent the transmembrane region in the amyloid precursor protein. The sequence of human Aβ-(1–42) is as follows: DAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIA. Soluble Aβ-(1–40) and Aβ-(1–42) are found in the cerebrospinal fluid and blood plasma of all humans where Aβ-(1–40) has a concentration of 5 nm in cerebrospinal fluid (7Lambert M.P. Barlow A.K. Chromy B.A. Edwards C. Freed R. Liosatos M. Morgan T.E. Rozovsky I. Trommer B. Viola K.L. Wals P. Zhang C. Finch C.E. Krafft G.A. Klein W.L. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 6448-6453Google Scholar, 8Vigo-Pelfrey C. Lee D. Keim P. Lieberburg I. Schenk D.B. J. Neurochem. 1993; 61: 1965-1968Google Scholar). It is yet to be established what triggers Aβ to convert from its soluble form to an amyloidogenic form, but it has been shown that physiological levels of Cu2+ and Zn2+ cause marked aggregation of Aβ. This process is thought to be the prelude to amyloid formation (9Bush A.I. Pettingell W.H. Multhaup G. Paradis M.D. Vonsattel J.P. Gusella J.F. Beyreuther K. Masters C.L. Tanzi R.E. Science. 1994; 265: 1464-1467Google Scholar). Levels of these metals are elevated in amyloid plaque deposits: 0.4 mm and 1 mm for Cu2+ and Zn2+, respectively (10Lovell M.A. Robertson J.D. Teesdale W.J. Campbell J.L. Markesbery W.R. J. Neurol. Sci. 1998; 158: 47-52Google Scholar). Cu2+-induced aggregation of Aβ occurs as the pH is lowered to 6.8. This mildly acidic environment mimics a feature of inflammation found in AD (11Atwood C.S. Moir R.D. Huang X. Scarpa R.C. M.A. Tanzi R.E. A.I. J. Biol. Chem. 1998; Scholar). Studies cerebrospinal fluid indicate that cause the aggregation of soluble Aβ peptide J. J. Neurochem. 1997; Scholar). chelators to Cu2+ and Zn2+ aggregation process X. C.S. Moir R.D. M.A. Vonsattel J.P. Tanzi R.E. A.I. J. Biol. Chem. 1997; Scholar, Huang X. C.S. Beyreuther K. Tanzi R.E. Masters C.L. A.I. J. Biol. Chem. 1999; Scholar). In addition, the neurotoxicity of Aβ is linked to and is a feature of the of AD M.A. G. Proc. Natl. Acad. Sci. U. S. A. 1997; Scholar). A role as a and in copper in a has been for Aβ peptide A. Biol. Scholar, X. C.S. M.A. Multhaup G. Scarpa R.C. M.P. J. Moir R.D. Tanzi R.E. A.I. 1999; Scholar, X. M.P. C.S. M.A. J.D. M. Multhaup G. Scarpa R.C. J. Moir R.D. C. Masters C.L. Tanzi R.E. A.I. J. Biol. Chem. 1999; Scholar, C.S. Huang X. Moir R.D. Tanzi R.E. A.I. Biol. 1999; Scholar, A.I. Curr. Opin. Chem. Biol. Scholar, 1998; Scholar, M.P. J. Biol. Chem. 1999; Scholar). There are to the role of copper in The is that AD is associated with elevated to It is to The concentration of copper the brain is to be a the brain has in to of which cause as and disease. There is evidence to suggest that for are in AD and AD is characterized by and in the brain M.P. 1997; Scholar). The is that the affinity of Aβ for Cu2+ is to these metals at extracellular This is also a extracellular levels of Cu2+ as as (10Lovell M.A. Robertson J.D. Teesdale W.J. Campbell J.L. Markesbery W.R. J. Neurol. Sci. 1998; 158: 47-52Google whereas that Aβ affinity for Cu2+ is at the and is to be in amyloid plaques C.S. Scarpa R.C. Huang X. Moir R.D. Tanzi R.E. A.I. J. Neurochem. Scholar). A using spectroscopy has direct evidence that copper and are bound the histidine in senile plaque J. C.S. M.A. G. Scholar). of the most significant of evidence to link copper with AD is the that amyloid deposits of brain from AD can be in by the of chelators to Cu2+ Huang X. C.S. Beyreuther K. Tanzi R.E. Masters C.L. A.I. J. Biol. Chem. 1999; Scholar). It has been shown that the of copper chelators can amyloid in AD and are in as for AD C.S. I. Huang X. Moir R.D. Beyreuther K. Tanzi R.E. Masters C.L. A.I. Scholar, A.I. Neurobiol. Scholar). A has shown that of copper in the of plaque Proc. Natl. Acad. Sci. U. S. A. Scholar, J. Science. Scholar). an of evidence to link Cu2+ with AD, the coordination and the residues involved in Cu2+ are yet to be and have been I. Beyreuther K. Masters C.L. A.I. J. Biol. Chem. Scholar). In addition, are as to the affinity and of both C.S. Scarpa R.C. Huang X. Moir R.D. Tanzi R.E. A.I. J. Neurochem. and A.K. Chem. 1999; for have been In a range of complementary spectroscopies to characterize the binding of Cu2+ to Aβ and the structural in Aβ copper spectroscopy have used the soluble of which the of the 29–42 are highly hydrophobic and are to be associated with direct coordination of the I. Beyreuther K. Masters C.L. A.I. J. Biol. Chem. Scholar, K. Scholar). In addition, have a of analogues of Aβ-(1–28) in which each of the histidine residues have been replaced with an and of the amyloid-β peptide by and by the at from the and the using and characterized using and 1H pH and each found to with Cu2+ mm used for electron paramagnetic whereas for 1H NMR and in and the pH using small of or The peptide using the of to the Scholar). the by The of or to the Aβ using small from Circular an Circular at a with a used for between and nm with A used for between and nm with a A of and from each used to using in to using the where the concentration and is the with a using a using a of nm and the range of in a and at affinity of l-histidine for Cu2+ is the affinity at pH is therefore or a of nm pH and or the affinity of glycine for Cu2+ is the affinity at pH is therefore or a of nm W.H. for Scholar). EPR using a at a of using a of a of at with a of G. in and at between and using a A of EPR shown have been from a with in the using or In to EPR using the by and J. it is to convert from to by using the where and is the in NMR using a 1H using the at in at a peptide concentration of 1 made by the of spectroscopy and of the spectroscopy and with of and of the N terminus as the amino whereas the C terminus as the at the C of the human sequence are shown in in a pH of Cu2+ 1 the EPR of of Cu2+ bound to Aβ-(1–28) a range of pH between 5 and The EPR at pH 5 a of of II or coordination The and are and the pH is a of are to with and of and with the of a of the at pH 5 in pH the of EPR have and at pH the The in with pH is shown as an in It is that at pH a of is and J. have shown that a of and can indicate The and at pH 5 are most of nitrogen and oxygen and coordination be pH the and are for We have complementary studies using for Aβ-(1–28) with Cu2+ at pH between and pH a is at nm nm which is of a II Cu2+ pH and the associated is and is the at nm as an is at pH and K. J. Chem. Scholar). as the pH is to pH is a at nm from Cu2+ The in the in the of in the of 1 of Cu2+ at and are for of Cu2+ D.B. Proc. Natl. Acad. Sci. U. S. A. 1999; Scholar, J. Biol. Chem. Scholar). these coordination as as histidine coordination the In these the contribution to is to the the is in a between J.M. J. Chem. Scholar). physiological pH and the of from the transition of the that coordination is It is that the pH and copper coordination by the main in a at In it is that Aβ a Type II square-planar coordination with and both EPR and indicate that the are highly a is at physiological and coordination is at pH of Cu2+ of Aβ-(1–28) with of Cu2+ have been in to the of copper binding to Aβ and are shown in of Cu2+ up to 1 are with a increase in 1 of is a to for the at 1 of Cu2+ and at of The in up to of of the EPR with a that all of the EPR for the are and therefore the of EPR The of a of copper up to 5 in increase in the of the EPR Cu2+ in a EPR at pH C.S. J. Scholar). We have by EPR of in at pH copper EPR are to Cu2+ bound to Aβ. of the EPR has been copper as shown as an in It is from the EPR that Aβ-(1–28) binds Cu2+ of Aβ-(1–28) with copper at physiological studies have been using both in the and of the at nm of and Aβ-(1–28) at of Cu2+ at pH In both and Cu2+ binding indicate Cu2+ of binding Aβ-(1–28) of the in the of is that amyloid formation in AD and amyloidogenic as disease are the of or peptide The Aβ peptide has a structural transition associated with amyloid with from to an Scholar). in the region can be used to in the the of and Aβ-(1–28) with the of of Cu2+ at pH Cu2+ binding to occurs as at pH the at nm is in as the pH is from pH to in the of with in the of Cu2+ that are significant in the between pH and pH the of Cu2+ causes a of the at nm and the of a at The of a contribution at nm is and is at pH a and which copper at pH and in the of Aβ-(1–28) with Cu2+ are as shown in A at nm and is by a of at The contribution at nm with copper is but is by the at which the of the Cu2+ to both and Aβ-(1–28) are shown as in The the in the in the with copper between and The residues to the C terminus have the The in the with the Cu2+ are by of which with the by EPR are at and and these are between and of a the be to at of The at nm is with the of copper between pH of and at nm is to or The of Aβ can therefore be to an increase in or The of a contribution at nm is of but indicate of the main of Copper to the physiological of Cu2+ binding to Aβ is its in have used the of glycine and l-histidine to Cu2+ affinity for Aβ by that the of Cu2+ to Aβ-(1–28) causes marked of the at glycine is it with Aβ for the and the as shown in Cu2+ to glycine the amino and with an Ka and glycine residues to a Cu2+ W.H. for Scholar). It of glycine to cause the to to its of the is at of the affinity of Cu2+ for Aβ-(1–28) is at an of that of the in the range have been using l-histidine as the In to its with of as shown in of histidine a Cu2+ using the amino and as with an at pH of This indicates that copper to Aβ-(1–28) with a affinity This the affinity of Cu2+ for Aβ but or a of nm but nm We have Cu2+ for Aβ-(1–28) using used to the at the of copper bound to glycine J. Biol. Chem. Scholar). We using the at nm that of glycine are to Cu2+ from Aβ-(1–28) as is by the have been for C.S. Scarpa R.C. Huang X. Moir R.D. Tanzi R.E. A.I. J. Neurochem. at of We that glycine or l-histidine have the binding of copper to a affinity This in a for the shown in have levels of Cu2+ to Aβ of is a affinity for copper associated with the of l-histidine have the the of 1 l-histidine to Aβ-(1–28) with of Cu2+ the to to its We can also with Cu2+ peptide and are for in EPR or In using both direct of from and have shown that the of Cu2+ to Aβ with a in the The of a affinity copper for Aβ-(1–28) has been Cu2+ of Aβ have been used to which residues are involved in binding to The histidine residues Aβ-(1–42) are thought to be the most for Cu2+ coordination physiological and is in the region and the EPR of and are A made a range of pH between and at 1 of In the of of the of and Aβ-(1–28) are also at all pH it is that residues have the binding of Cu2+ to Aβ at 1 or of Cu2+ a range of pH The in the of and Aβ-(1–28) nm are to the of in the of the of In the of and are from and as shown in In at pH and Aβ-(1–28) associated with whereas has a at nm and has a at The of that the N terminus and/or His6 are involved in copper In addition, indicate that His13 and/or His14 are residues in the Cu2+ A in the EPR between and copper of the are but are to an Type II Cu2+ The pH of binding is for and EPR the of indicates that the transition between the pH and coordination mode occurs at a pH for with a of Aβ-(1–28) and the residues involved in the coordination of analogues have been in which each of the histidine residues has been replaced with an alanine peptide has also been in which the N terminus is by It is that from these are the most for copper The EPR of all analogues indicate Cu2+ coordination nitrogen and oxygen ligands. pH in the between all of the analogues and Aβ-(1–28) are at pH the of the analogues are In as shown in is a pH to the of The EPR suggest that the at the pH the of all of the residues and the N-terminal amino have used a of to coordination and are can be to the coordination the Cu2+ with are to the of with in the and of J.M. J. Chem. Scholar). The of the peptide and for the Aβ-(1–28) are shown in have been at pH and for all analogues as as In addition, have been with both 1 and of Cu2+ associated with the Cu2+ are at of nm to copper nm to Cu2+ nm to nitrogen to Cu2+ and nm to Cu2+ K. J. Chem. Scholar). each in with 1 of at pH the a to that the N terminus is for In a at and the at nm by to the a The of are also to the In is a in at nm but with an increase in the The of has to the with small in of the at It is the small in for the at nm is significant or to or small in the between and the are with a small in the at these it that at 1 of His13 and the N terminus the copper Cu2+ coordination to His14 and His6 is from the but be it is from the in the region as shown in and that His14 and His6 are involved in region of Aβ-(1–28) and Aβ with the of 1 of pH are Copper each of the analogues also using in the region and with the the of each of the analogues and the 1 of Cu2+ analogues from Aβ-(1–28) and of the analogues at In addition, the at nm is for the analogues to the and is to This therefore the N-terminal amino in the coordination of the of Cu2+ but also all histidine In a to the involved in copper the affinity for each of the analogues using glycine and in the of glycine indicates that and Aβ-(1–28) have affinity for with glycine a to at of Aβ-(1–28) a in affinity for This the studies that indicate the N terminus is a for copper a the of between 5 and of a at of that has an affinity for copper with the coordination of The with the His6 also a in affinity for Cu2+ with of glycine to a Aβ-(1–28) analogues with His13 or His14 a in affinity to the with a of with of glycine in each In with the shown in the affinity of Cu2+ for Aβ-(1–28) is by of the N terminus or the of of the histidine 1H NMR has been used to The of Aβ-(1–28) of a Cu2+ 1H NMR in to or to the of the and for all histidine residues of Aβ-(1–28) at pH to the In which has been as a to Cu2+ I. Beyreuther K. Masters C.L. A.I. J. Biol. Chem. Scholar, K. is by Cu2+ and for is to be involved in direct coordination to the Cu2+ The Cu2+ are between peptide to all of the Aβ with of Cu2+ The of of the copper between that the indicate what of Cu2+ is to the copper it is possible to between affinity copper coordination and a small of the copper for a histidine It is therefore from the NMR the of each histidine is to a or a affinity binding It that the of of the Tyr10 indicates that it can be as a possible in the coordination of the 1H NMR with in both the and as as the glycine studies of all of the Aβ a of the for Cu2+ coordination of the of Cu2+ to Aβ. indicate the coordination of the N terminus of Aβ and and His6 are also but has been that is histidine between Cu2+ in the Aβ-(1–28) Cu2+ I. Beyreuther K. Masters C.L. A.I. J. Biol. Chem. Scholar). This the that the EPR with Cu2+ pH and that to electron a histidine as is in EPR of Proc. Natl. Acad. Sci. U. S. A. 4245-4249Google Scholar). have of EPR with copper EPR in which electron is are and is in these have been for Aβ-(1–28) with of Cu2+ a range of between and but are by in We suggest that the in I. Beyreuther K. Masters C.L. A.I. J. Biol. Chem. to at copper concentration in a for of a a of histidine residues has been K. Chem. Scholar). In copper to the of both a coordination to the copper in a square-planar of the coordination of the N terminus and His6 coordination to copper from histidine it for the or for or The of coordination is by the at which for The of transition J.M. J. Chem. and that is coordination at physiological pH and as A of Aβ using spectroscopy indicates at mildly acidic and coordination at physiological pH and K. Scholar). coordination the coordination the between the and the R. Chem. 82: Scholar). This transition between and coordination with pH is by our studies that indicate coordination at pH the possible the Cu2+ in a square-planar the N-terminal amino and of His13 and The is from His6 in the role of Cu2+ in AD C.S. Scarpa R.C. Huang X. Moir R.D. Tanzi R.E. A.I. J. Neurochem. Scholar, J. C.S. M.A. G. Scholar, Proc. Natl. Acad. Sci. U. S. A. Scholar, J. Science. Scholar, A.I. Masters C.L. Tanzi R.E. Proc. Natl. Acad. Sci. U. S. A. have used a range of complementary EPR, and to Cu2+ binding to the Aβ In Cu2+ binds to the N terminus of Aβ and the histidine but as shown in Aβ is a peptide in whereas the amyloid form of the peptide is rich in Scholar). We therefore in the that Cu2+ chelation a in Aβ. We have shown that the N-terminal to coordination the N-terminal amino as as His13 and copper chelation of the studies of Aβ-(1–28) indicate copper a In addition, of and Aβ-(1–28) indicate that residues are by copper coordination in its soluble We have shown that His13 is a critical in the Cu2+ a histidine at and aggregation of Aβ is (11Atwood C.S. Moir R.D. Huang X. Scarpa R.C. M.A. Tanzi R.E. A.I. J. Biol. Chem. 1998; Scholar). human Aβ can with It has been shown that copper coordination has a the of Aβ (11Atwood C.S. Moir R.D. Huang X. Scarpa R.C. M.A. Tanzi R.E. A.I. J. Biol. Chem. 1998; Scholar). The N-terminal amino acids of Aβ and the histidine residues and the N-terminal amino Cu2+ coordination cause the of all copper binding have a the of the Aβ peptide with a in Aβ and a from an to a highly N-terminal It is that in residues is the cause of the aggregation Cu2+ We have shown that coordination of Cu2+ to Aβ is highly pH-dependent. It is that is a transition between coordination as the pH is In the of the is pH This with a which a transition between a and at pH M. K. J. 95: Scholar). A by that Cu2+ aggregation of Aβ as the pH is lowered from physiological pH to pH (11Atwood C.S. Moir R.D. Huang X. Scarpa R.C. M.A. Tanzi R.E. A.I. J. Biol. Chem. 1998; Scholar). The in coordination geometry, to the of coordination at pH be to the pH of the aggregation in the of to the physiological for Cu2+ binding to Aβ is its The concentration of extracellular Cu2+ is in blood with extracellular levels of Cu2+ as as (10Lovell M.A. Robertson J.D. Teesdale W.J. Campbell J.L. Markesbery W.R. J. Neurol. Sci. 1998; 158: 47-52Google Scholar). Cu2+ for Aβ-(1–28) are or of that of the extracellular copper This that Aβ has affinity to copper at physiological levels of of Aβ for copper studies by the Cu2+ affinity at and for Aβ-(1–40) and respectively (11Atwood C.S. Moir R.D. Huang X. Scarpa R.C. M.A. Tanzi R.E. A.I. J. Biol. Chem. 1998; Scholar). This using to an affinity for Aβ-(1–42) C.S. Scarpa R.C. Huang X. Moir R.D. Tanzi R.E. A.I. J. Neurochem. Scholar). have a affinity of for Aβ-(1–42) A.K. Chem. 1999; Scholar). of nm between these but is to that by A.K. Chem. 1999; Scholar). Copper binding from EPR suggest copper of Aβ at of We are of of the of copper binding to Aβ, of which a A.K. Chem. 1999; Scholar). in with our have copper at for both Aβ-(1–40) and with a affinity at of Cu2+ C.S. Scarpa R.C. Huang X. Moir R.D. Tanzi R.E. A.I. J. Neurochem. Scholar). in the of between and 1 of both our EPR and indicate that Aβ-(1–28) form a these In addition, from our EPR evidence of Aβ-(1–28) using histidine coordination to form a as I. Beyreuther K. Masters C.L. A.I. J. Biol. Chem. Scholar). The of Cu2+ for Aβ by C.S. Scarpa R.C. Huang X. Moir R.D. Tanzi R.E. A.I. J. Neurochem. the in the We suggest that the Cu2+ binding by for Aβ-(1–42) and for Aβ-(1–28) the soluble form of The mode of binding copper in be from that found in plaques. C.S. Scarpa R.C. Huang X. Moir R.D. Tanzi R.E. A.I. J. Neurochem. a whereas evidence of a for Aβ-(1–28) in solution. is a The for Aβ-(1–42) to form and a It is that soluble Aβ-(1–42) a as is for The hydrophobic residues 29–42 to from which has been by a using spectroscopy K. in which a residues 29–42 which to Cu2+ the residues aggregation that a copper of Aβ. There have been structural studies of the The paramagnetic copper has the of an NMR Studies using spectroscopy have that Cu2+ binds to the of the histidine and the nitrogen mildly acidic K. Scholar, K. Scholar). studies In with our and NMR and glycine the that all to in with our Tyr10 but the N terminus in coordination K. Scholar). In with our studies of Aβ M. K. J. 95: the N terminus in binding studies now evidence to link Cu2+ with has direct evidence that copper and are bound the histidine of Aβ in senile plaque J. C.S. M.A. G. Scholar). In addition, copper chelators can amyloid plaques and represent possible for Alzheimer's copper chelators can amyloid in C.S. I. Huang X. Moir R.D. Beyreuther K. Tanzi R.E. Masters C.L. A.I. Scholar). Copper is also linked with the neurotoxicity of Aβ and free radical associated with Alzheimer's disease A. Biol. Scholar). of copper in the have been shown to plaques and in a of Alzheimer's disease Proc. Natl. Acad. Sci. U. S. A. Scholar). that our studies have made a significant contribution to understanding Cu2+ binding of Aβ in by the the Cu2+ and the of pH the binding mode and of the main of Aβ. We the NMR at the for for the of NMR We for the of the at of and also and for