Abstract: The invention relates to a method for production of an activated biochip for covalent fixing of oligonucleotide probes to a solid support by means of a spacer compound of the NHS-PEG-VS type and biochips produced by the above method. The invention further relates to methods for detection of nucleic acids in a sample or methods for screening compounds which may be specifically bound to oligonucleotide probes in which said biochips are used. The invention also relates to detection kits for quantitative or qualitative analysis of nucleic acids in a sample comprising said biochips and use of the above as affinity matrix for purification of nucleic acids, for sequencing nucleic acids, for the qualitative or quantitative analysis of the expression of genes or for the study and detection of genetic polymorphism.