JOINT FILING AGREEMENT

                                                                       EXHIBIT 1
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                             JOINT FILING AGREEMENT

         Each of the undersigned hereby acknowledges and agrees, in compliance
with the provisions of Rule 13d-1(k)(1) promulgated under the Securities
Exchange Act of 1934, as amended, that the Schedule 13D to which this Agreement
is attached as an Exhibit (the "Schedule 13D"), and any amendments thereto, will
be filed with the Securities and Exchange Commission jointly on behalf of the
undersigned. This Agreement may be executed in one or more counterparts.

Dated:  November 8, 2004



                                PERSEUS 2000, L.L.C.

                                By:     Perseus 2000 Management, L.L.C.
                                        Managing Member

                                By:     Perseus EC, L.L.C.
                                        Managing Member

                                By:     /s/ Xxxx Xxxxxxx
                                        ---------------------------------------
                                        Name:  Xxxx Xxxxxxx
                                        Title: Secretary and Treasurer


                                PERSEUS 2000 MANAGEMENT, L.L.C.

                                By:     Perseus EC, L.L.C.
                                        Managing Member

                                By:     /s/ Xxxx Xxxxxxx
                                        ---------------------------------------
                                        Name:  Xxxx Xxxxxxx
                                        Title: Secretary and Treasurer


                                PERSEUS EC, L.L.C.


                                By:     /s/ Xxxx Xxxxxxx
                                        ---------------------------------------
                                        Name:  Xxxx Xxxxxxx
                                        Title: Secretary and Treasurer


                                PERSEUSPUR, L.L.C.


                                By:     /s/ Xxxx Xxxxxxx
                                        ---------------------------------------
                                        Name:  Xxxx Xxxxxxx
                                        Title: Secretary and Treasurer



                                 /s/ Xxxx Xxxxxxx, Attorney-in-Fact
                                 ----------------------------------------------
                                 XXXXX X. XXXXX