Abstract: The present invention provides for a method for isolating and partially characterizing the nucleotide sequence for a novel polypeptide chain of human basement membrane (type IV) collagen, referred to as the .alpha.5(IV) polypeptide chain. The invention provides for the use of the identified nucleotide sequence (or DNA fragments thereof) to detect mutations in individual genes specific for the .alpha.5(IV) chain which can, directly or indirectly, produce several human diseases. Moreover, the invention also relates to procedures for determining genetic or acquired disorders of basement membranes using the identified nucleotide sequence (or DNA fragments thereof) of the .alpha.5(IV) polypeptide chain, probes specific to DNA fragments of said nucleotide sequence,or antibodies to the nucleotide sequence or DNA parts thereof.

Abstract: This process involves the use of benzoquinone as cross-linking agent in large excess compared with the substance to be activated. The activation reaction is realized in a homogeneous liquid medium. Said process making it possible for example to couple antibodies to enzymes for determining or detecting said antibodies.The process can be used for the determination of antitetanic antibodies in human serum.