Abstract: Tripeptide derivatives, characterized by the general formula:R.sub.1 --X--D--Arg--A--Arg--NH--R.sub.2wherein R.sub.1 is hydrogen, .alpha.- or .beta.-naphtyl residue, lower alkyl residue which may be substituted with a carboxyl group, unsubstituted or substituted phenyl- or phenylalkyl residue. ##STR1## or a single bond with the proviso that when R.sub.1 is hydrogen then and only then X is a single bondA=Gly or SarR.sub.2 =an aromatic or heterocyclic residue which gives a compound R.sub.2 --NH.sub.2 by enzymatic hydrolysis, which can be determined quantitativelyor disalts and trisalts of inorganic or organic acids thereof, process for their preparation and method for determination of serine proteases, especially Factor X.sub.a,or components which can interact with serine proteases or zymogen forms thereof.

Abstract: New thrombin inhibiting N.sup..alpha. -arylsulfonyl-p-guanidinophenylalanine amides of the formula ##STR1## wherein Ar is a substituted aryl and R.sub.1 and R.sub.2 are an alkyl group having 1-5 carbon atoms or together with the amine nitrogen form an heterocyclic ring, in racemate form as well as in form of optical active antipodes, theirs pharmaceutically acceptable salts, methods for their preparation, pharmaceutical composition and diagnostical preparation containing these compounds, use of the compounds in treatments of thrombosis and methods of treatment of thrombosis as well as methods for determination of thrombin concentration in blood.

Abstract: Method for the quantitative determination of serine proteases which includes contacting the substance for which the determination is desired with a diagnostically active chromogenic substrate with good stability and high specificity to serine proteases having the formula: H--D--A.sub.1 --A.sub.2 --A.sub.3 --NH--R or salts thereof, wherein A.sub.1 is Gly, Ala, Val, Leu, Ile, Pip, Pro, or Aze; A.sub.2 is Gly, Ala, Val, Leu, Ile, Pip, Pro, Aze, or Phe; A.sub.3 is Arg, Lys, or Orn, and R is a chromophoric group.

Abstract: Diagnostically active chromogenic substrate with good stability and high specificity to serine proteases having the formula: H-D-A.sub.1 -A.sub.2 -A.sub.3 -NH-R or salts thereof, wherein A.sub.1 is Gly, Ala, Val, Leu, Ile, Pip, Pro, or Aze; A.sub.2 is Gly, Ala, Val, Leu, Ile, Pip, Pro, Aze, or Phe; A.sub.3 is Arg, Lys, or Orn, and R is a chromophoric group.