The assets of the system shall be invested as one fund, and no particular person, group of persons or entity shall have any right in any specific security or property or in any item of cash, other than an undivided interest in the whole except as otherwise provided in this Article.
     The changes to this Section and Sections 15-155, 15-167 and 15-172 made by this amendatory Act of 1989, and Section 15-167.2, shall be applicable to all participants, annuitants and beneficiaries now or hereafter covered by this Article.