Chromogenic Substrates

Can the tPA activity standard be used to measure two-chain tPA or just single chain tPA?

The t-PA 10 mg activity standard is composed 95% of single-chain t-PA with a specific fibrin...

Define a katal.

One katal (kat) is the amount of enzyme that converts one mole of substrate per second. Acti...

Define an enzyme and a substrate.

Enzymes are proteins that catalyze most of the chemical reactions that take place in the bod...

How can I measure prothrombin activity? What is considered an elevated level of prothrombin activity?

A mutation G ® A in the untranslated 3? region of the prothrombin gene at nucleotide positi...

I am looking for a chromogenic assay to measure TFPI activity. What substrates will work?

TFPI is a direct inhibitor of FXa, and the TFPI/FXa complex inhibits TF/FVIIa. The chromogen...

Is the plasminogen reagent Glu- or Lys- plasminogen?

It is a preparation of at least 95% Glu-plasminogen.

The activity of plasmin and plasminogen is expressed in CU. What is this, and what is the equivalent in nkat?

CU stands for Casein Units, and is a measure of the proteolytic activity on the substrate ca...

The factor Xa reagent says it is 71 nkat, but I need to know what that is in g/ml and mol/ml.

One katal (kat) is the amount of enzyme that converts one mole of substrate per second. Acti...

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?

The Chromogenix line is geared toward the proteins involved in hemostasis. These are a group...

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 substrates for plasmin include S-2251, S-2302, S-2390 (discontinued in the 25 mg quantit...

What aspects must a scientist consider when choosing the best chromogenic substrate?

Synthetic substrates are very sensitive; they can detect very low enzyme activities and are...

What if the reconstituted substrate has some precipitate or is cloudy?

The substrate solution is usually prepared with sterile water, but sometimes they may not di...

What is a chromogenic substrate composed of?

Chromogenic substrates are peptides that react with proteolytic enzymes under the formation...

What is a peptide? What is the difference between a tripeptide and a tetrapeptide? How are amino acids linked to form peptides?

A peptide is the name assigned to short polymers of amino acids. They are classified by the...

What is the 53 nkat vial of thrombin equivalent to in NIH units?

Based on an assay with S-2238, for bovine thrombin,1 NIH-U = 1.15 IU = 3.4 nkat. According t...

Which substrate is best suited for measuring two-chain tPA, and why?

S-2765, S-2366, and S-2288, S-2403 are suitable for single-chain tPA, and S-2251 is used in...

Why are the reactions measured at 405 nm?

The absorption intensity is expressed by the Beer-Lambert law, A = e x c x l, where A is abs...

Why is pNA the leaving group on all of the Chromogenix substrates?

A good chromophore must be readily cleaved by and dissociated from the enzyme. The color mus...