Fcabs are antibodies fragments engineered from the constant region of an antibody (Fc). In naturally occurring antibodies (such as IgGs), the antigen-binding sites are located at the variable regions (Fab).
Fcabs can be expressed as soluble proteins or they can be engineered back into a full IgG. This type of antibodies are therefore able to recognise two different antigens, one at their Fab region and a second one at the Fc region, hence the name of bispecific antibodies. This antibody fragment is part of the modular antibody technology of F-star Biotechnology Ltd.
The Ferrocarril de Antofagasta a Bolivia (British company name: Antofagasta (Chili) & Bolivia Railway or FCAB for short) is a private railway operating in the northern provinces of Chile. It is notable in that it was one of the earliest railways built to 2 ft 6 in (762 mm) narrow gauge, with a route that climbed from sea level to over 4,500 m (14,764 ft), while handling goods traffic totaling near 2 million tons per annum. It proved that a railway with such a narrow gauge could do the work of a standard gauge railway, and influenced the construction of other railways such as the Estrada de Ferro Oeste de Minas. It was later converted to 1,000 mm (3 ft 3 3⁄8 in) metre gauge, and still operates today.
The railway started at the Chilean port of Antofagasta. It proceeded up the front range of the Andes to Ollagüe on the Bolivian border, then across the Bolivian pampas to Uyuni and Oruro. At Oruro, the gauge changed to 1,000 mm (3 ft 3 3⁄8 in) metre gauge for the remainder of the route to La Paz, the capital of Bolivia. A number of branches were added to reach various mining fields. The Collahuasi branch reached 4,815 m (15,797 ft) above sea level, regarded at the time of construction as the highest railway in the world. The total length of the 2 ft 6 in (762 mm) gauge lines, including branches and subsidiaries, was 1,537 km (955 mi).