Exhibit 99.1350CERT

         Certification Pursuant to Section 906 of the Sarbanes Oxley Act

I, Robert C. Doll, Jr., Chief Executive Officer of Merrill Lynch Core Principal
Protected Fund of Merrill Lynch Principal Protected Trust and Master Large Cap
Core Portfolio of Master Large Cap Series Trust (together, the "Fund"), certify
that:

      1.    The N-CSR of the Fund (the "Report") fully complies with the
            requirements of Section 13(a) or 15(d) of the Securities Exchange
            Act of 1934; and

      2.    The information contained in the Report fairly presents, in all
            material respects, the financial condition and results of operations
            of the Fund.

Dated: June 20, 2005


                                        /s/ Robert C. Doll, Jr.
                                        -----------------------
                                        Robert C. Doll, Jr.,
                                        Chief Executive Officer of
                                        Merrill Lynch Core Principal Protected
                                        Fund of Merrill Lynch Principal
                                        Protected Trust and Master Large Cap
                                        Core Portfolio of Master Large Cap
                                        Series Trust

A signed original of this written statement required by Section 906, or other
document authenticating, acknowledging, or otherwise adopting the signature that
appears in typed form within the electronic version of this written statement
required by Section 906, has been provided to Merrill Lynch Core Principal
Protected Fund of Merrill Lynch Principal Protected Trust and Master Large Cap
Core Portfolio of Master Large Cap Series Trust and will be retained by Merrill
Lynch Core Principal Protected Fund of Merrill Lynch Principal Protected Trust
and Master Large Cap Core Portfolio of Master Large Cap Series Trust and
furnished to the Securities and Exchange Commission or its staff upon request.



Exhibit 99.1350CERT

         Certification Pursuant to Section 906 of the Sarbanes Oxley Act

I, Donald C. Burke, Chief Financial Officer of Merrill Lynch Core Principal
Protected Fund of Merrill Lynch Principal Protected Trust and Master Large Cap
Core Portfolio of Master Large Cap Series Trust (together, the "Fund"), certify
that:

      1.    The N-CSR of the Fund (the "Report") fully complies with the
            requirements of Section 13(a) or 15(d) of the Securities Exchange
            Act of 1934; and

      2.    The information contained in the Report fairly presents, in all
            material respects, the financial condition and results of operations
            of the Fund.

Dated: June 20, 2005


                                        /s/ Donald C. Burke
                                        -------------------
                                        Donald C. Burke,
                                        Chief Financial Officer of
                                        Merrill Lynch Core Principal Protected
                                        Fund of Merrill Lynch Principal
                                        Protected Trust and Master Large Cap
                                        Core Portfolio of Master Large Cap
                                        Series Trust

A signed original of this written statement required by Section 906, or other
document authenticating, acknowledging, or otherwise adopting the signature that
appears in typed form within the electronic version of this written statement
required by Section 906, has been provided to Merrill Lynch Core Principal
Protected Fund of Merrill Lynch Principal Protected Trust and Master Large Cap
Core Portfolio of Master Large Cap Series Trust and will be retained by Merrill
Lynch Core Principal Protected Fund of Merrill Lynch Principal Protected Trust
and Master Large Cap Core Portfolio of Master Large Cap Series Trust and
furnished to the Securities and Exchange Commission or its staff upon request.