Frequently Asked Questions
- What is a chromogenic substrate?
- What is a peptide? What is the difference between a tripeptide and a tetrapeptide? How are amino acids linked to form peptides?
- Define an enzyme and a substrate.
- What is a chromogenic substrate composed of?
- Define a katal.
- What aspects must a scientist consider when choosing the best chromogenic substrate?
- Why are the reactions measured at 405 nm?
- Why is pNA the leaving group on all of the Chromogenix substrates?
- What if the reconstituted substrate has some precipitate or is cloudy?
- Which substrate is best suited for measuring two-chain tPA, and why?
- There are a few different substrates that are hydrolyzed by plasmin. If I want to use as short incubation times as possible, and need a selective substrate for plasmin, which should I choose?
- The majority of the Chromogenix substrate library has an Arginine (Arg or R) group at the P1 position (the amino acid position that occurs at the preferred cleavage site). Why is this?
- If I want to determine FX in plasma, but do not want to buy a kit, what other options are there?
- The factor Xa reagent says it is 71 nkat, but I need to know what that is in g/ml and mol/ml.
- What is the 53 nkat vial of thrombin equivalent to in NIH units?
- The activity of plasmin and plasminogen is expressed in CU. What is this, and what is the equivalent in nkat?
- Is the plasminogen reagent Glu- or Lys- plasminogen?
- What constitutes the tPA stimulator, and how is it prepared?
- Can the tPA activity standard be used to measure two-chain tPA or just single chain tPA?
- The tPA standard dilution of 10 IU/ml is confusing in the Coaset tPA kit. Can you explain it?
- I am looking for a chromogenic assay to measure TFPI activity. What substrates will work?
- How can I measure prothrombin activity? What is considered an elevated level of prothrombin activity?