Fig. 1.
Design of the virus laser. a Model of the atomic structure of a lasing detection probe composed of M13 bacteriophage (PDB: 2MJZ) covalently modified with fluorescein isothiocyanate isomer 1 (FITC) dyes (PubChem CID: 18730, green).29,57,58 There are ~540 rings of gene 8 coat proteins per M13, but only 13 are shown here. The target biomolecule is a IgG2a monoclonal antibody (mAb) that can be bound by the gene 3 coat proteins and is represented in the figure by the structure of an intact IgG2a mAb (PDB: 1IGT) which should have a homologous structure.59 Rectangular zoomed area, image of the surface of M13 showing the close proximity of the attached dyes. Circular zoomed area, chemical structure of fluorescein isothiocyanate. Fluorescein has shorter moieties bonded to the aromatic ring system than other xanthene dyes, such as rhodamine 6G, reducing the likelihood of contact quenching between neighbouring dyes. b Optical configuration for experiments conducted using resonant cavity R2 (Supplementary Fig. 1). The excitation source was an optical parametric oscillator (OPO), the detector was a photomultiplier tube (PMT) and the emission was attenuated by neutral density (ND) filters. Inset, photograph of the emission from the gain medium of the virus laser (green light) as viewed from along the axis of the resonator