Frequently Asked Questions
Below are answers to the most frequently asked questions about our products and services. If you have a question that is not answered feel free to contact us. Our technical specialists are happy to help with any questions you might have about our products.
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Gold Nanoparticles
- How do I wash my gold nanoparticles?
- What gold nanoparticle size should I choose for my application?
- My gold nanoparticle settle out of solution upon storage. Is this normal?
- What is the shelf life of the gold nanoparticles?
- The gold nanoparticle solution turns violet when I add salt containing buffer. Why is that?
- Why is your functionalized gold nanoparticles so expensive compared to your standard gold nanoparticles?
Trilite™ Fluorescent Nanocrystals
- The amount of your fluorescent nanocrystals are given in mg. How many particles does this correspond to?
- What is the molecular weight of your quantum dots?
- What is the quantum efficiency of your quantum dots?
Fluorescent Dyes
- What is the correction factor at 280nm for your Cyto dyes?
- Where can I find a protocol for conjugation of a protein to your Cyto NHS dyes?
Ordering and Shipping
Other
How do I wash my gold nanoparticles?For most applications our gold nanoparticles can be used without any additional washing steps. If you have a sensitive application that requires additional washing the best way to do so is by either centrifugation or filtration. For recommended centrifugation speeds and times please refer to Storage & Handling of gold nanoparticles - Tech Note #101.
What gold nanoparticle size should I choose for my application?The size of gold nanoparticle to use is very depandent upon the intended application. Generally smaller particles offer better sensitivity in applications such as immunogold labeling due to less steric hindrance and the ability to bind more gold nanoparticles to the desired target. However, small gold nanoparticles are less visible than larger particles which must be taken into account. For example, particles with a size between 30-50nm are particularly useful for development of rapid tests such as lateral flow assays.
My gold nanoparticle settle out of solution upon storage. Is this normal?Settling of gold nanoparticles on the bottom of the storage flask is completely normal and is especially common for larger sized particles, which settles at greater speed. Settling does not affect the performance of the particles. Prior to use, simply swirl the solution to properly disperse your gold nanoparticles and obtain a homogenous solution.
What is the shelf life of the gold nanoparticles?Our gold nanoparticles are stable for at least 1 year if stored unopened and as specified at 4 degrees.
The gold nanoparticle solution turns violet when I add salt containing buffer. Why is that?Due to repulsive forces arising from the surface charge of gold nanoparticles, an energy barrier must be overcome for individual particles to interact. When no (or small) amounts of electrolytes such as NaCl is present, this energy barrier is too strong for interaction to occur between particles. However, upon addition of NaCl this energy barrier is reduced allowing the gold nanoparticles to interact and aggregate. This aggregation causes a phenomenon called surface-plasmon coupling which changes the adsorption maximum of light to a higher wavelength resulting in a change in color of the solution.
Why is your functionalized gold nanoparticles so expensive compared to your standard gold nanoparticles?Our pegylated gold nanoparticles are concentrated 50 times compared to our non-functionalized gold and 1ml of 50OD functionalized particles thus represent 50 ml of standard gold nanoparticles. In addition, making our functionalized gold takes additional time, and considerable effort is put into quality control to assure you get the best functionalized gold available.
The amount of your fluorescent nanocrystals are given in mg. How many particles does this correspond to?The number of nanocrystals per mg is 1.2x1015.
What is the molecular weight of your quantum dots?All of our quantum dots have the same size with a molecular weight of 650,000 Da.
What is the quantum efficiency of your quantum dots?The quantum efficiency of our quantum dots is 55-65% (alkyl functional fluorescent nanocrystals compared to laser dyes). Our water soluble quantum dots have 15% lower quantum efficiency compared to the alkylated fluorescent nanocrystals.
What is the correction factor at 280nm for your Cyto dyes?The average correction factor at 280nm for our Cyto dyes is 0.09. Use this factor to compensate for absorbance contributed by the Cyto dye at 280nm when determining the concentration of your fluorescently labeled protein at this wavelength.
Where can I find a protocol for conjugation of a protein to your Cyto NHS dyes?A starting protocol for conjugation of one of our Cyto NHS-dyes to a protein can be found here
How much do you charge for shipping?For information regarding our shipping policy and costs you can read our ordering and shipping details page.
Can I place an order using a credit card?We are happy to accept orders placed with VISA and Mastercard, as well as standard purchase orders. For more information please refer to our ordering and shipping details page.
What is USP grade water?USP grade water is distilled water intended for use as an ingredient of official preparations and in tests and assays. It has a conductivity of 0.91uS/cm and is purified under good manufacturing processes and meets the requirement of US Pharmacopeia.
