Presolicitation Notice: HEALTH AND HUMAN SERVICES, DEPARTMENT OF, NATIONAL INSTITUTES OF HEALTH, NATIONAL INSTITUTES OF HEALTH NIAID is planning to procure a rotor package specific to the requirements of NIAID to accompany an Optima XE-90 ultracentrifuge. This procurement is intended to support the PREMISE program of the Vaccine Research Center in characterizing macromolecules and nanoparticles for the detection of specific antibodies directed towards a panel of respiratory virus spikes/glycoproteins. The rotor package, provided by Franklin Young International Inc on their GSA contract, is a Beckman-Coulter Vti-50.1 rotor package 12 x 39 mL, capable of running density gradients in shorter time spans compared to older models. The acquisition will not be split between vendors, and the sole source requirement is justified under 41 U.S.C. 1901 (a) (1) as implemented by FAR 13.106-1. All responsible sources that can provide comparable services may submit a capability statement for consideration.