Quality Biological, Inc.

Common Questions:

The following are questions frequently addressed to Quality Biological's Customer Service and Technical Service personnel. They are provided here to assist in your choice and use of Quality Biological products for cell and molecular biology research.

Cell Biology FAQ’s

Question: Should I supplement Quality Biological serum-free media (SFM) with L-glutamine prior to use? If so, what should be the final concentration of L-glutamine?

Answer: We recommend that Quality Biological SFM be supplemented with L-glutamine to a final concentration of 1-3 mM prior to use. Studies indicate that L-glutamine containing media, even when stored at +4° C, is stable for only 3 weeks. At higher temperatures, this particular amino acid is far less stable.

Question: How stable are your sera and basal media?

Answer: If our sera are stored properly, namely at -10 to -20° C, they should be acceptable for use up to 48 months. With the exception of DMEM, all other basal media stored at +4° C will have a 2-year expiration date. However, DMEM even at refrigerated temperatures, tends to precipitate after 1 year.

Question: What is the pH of your Cell Culture Grade water?

Answer: In general, water has an extremely low buffering capacity. It is not unusual for water to range in pH from 2 to 10 units.

Question: How do I adapt my cells from a serum-containing medium to one of your serum-free media (SFM)?

Answer: Basically, there are two ways:
The "Weaning Method" and "The Quick Method." These are described in the Quality Biological Catalog. In addition, a separate document describing these two methods and other aspects of serum-free cell culture is available. Click on Serum Free Medium Cell Culture to view or print the document.

Question: I am interested in your custom cell biology products. What are your minimum requirements for customized reagents?

Answer: We are committed to providing the very best custom manufacturing service and we are pleased to assist with both small and large volume requirements. If the product of interest must be sterile filtered, our minimum requirement is 25L; whereas for products that can be autoclaved, our minimum is only 5L. Custom products can be packaged into 1mL to 20L size containers.

Molecular Biology FAQ’s

Question: What is the pH of your DEPC-treated Water and Molecular Biology Grade Water?

Answer: In general, water has an extremely low buffering capacity. It is not unusual for water to range in pH from 2 to 10 units.

Question: What is the difference between your SOC and SOB media?

Answer: SOC contains 20mM glucose whereas SOB has none.

Components
	SOB	SOC
KCl	0.19 g/L	0.19 g/L
Mg²⁺	20.0mM*	20.0mM*
NaCl	0.58 g/L	0.58 g/L
Tryptone	20.00 g/L/TD	20.00 g/L
Yeast Extract	5.00 g/L	5.00 g/L
D-glucose	0	3.60 g/L

*Omitted from preparation. Add 20mM of MgCl₂ prior to use.

Question: What is the difference between your Lennox L and Luria-Bertani media?

Answer: The difference between these two bacteriological media is their respective sodium chloride concentrations. Lennox L broth contains 5.0 g/L NaCl as opposed to Luria-Bertani which has 10.0 g/L of sodium chloride.

Components
	Lennox L	Luria-Bertani
Yeast Extract	5.00 g/L	5.00 g/L
Tryptone	10.00 g/L	10.00 g/L
NaCl	5.00 g/L	10.00 g/L

Question: What is the formulation of your TE buffers?

Answer: Regardless of whether our product is TE, pH 8.0 or TE, pH 7.4, the concentrations of Tris (T) and EDTA (E) are 10mM and 1mM respectively. Click on TIS to access the library of Technical Information Sheets for more information.

Question: Is your Prehybridization/Hybridization buffer qualified for RNA?

Answer: Our Prehybridization/Hybridization Buffer is qualified for DNA applications only (e.g. Southern Blotting). Click on TIS to access the library of Technical Information Sheets for more information.

For RNA applications (e.g. Northern Blotting), we recommend our Hybridization Buffer for Nylon Membranes. Click on TIS to access the library of Technical Information Sheets for more information.

Question: How do you remove "DEPC" from your DEPC-treated water?

Answer: Our DEPC (Diethyl pyrocarbonate) elimination process is proprietary. However, once we remove the DEPC from our DEPC-treated water, it is sterile filtered through 0.1 µm filter into 100 and 1L plastic (PET) bottles. Click on TIS to access the library of Technical Information Sheets for more information.

Question: What are the compositions of your RNA, DNA, and SDS-Protein Gel Loading Solutions?

Answer: See the table below.

Components	RNA Gel Loading Solution, 10X	DNA Gel Loading Solution, 5X	SDS Protein Gel Loading Solution, 2X
Bromophenol Blue	0.25% (w/v)	0.25% (w/v)	0.2% (w/v)
Xylene cyanole FF	0.25% (w/v)	0.25% (w/v)	-
EDTA	1mM	-	-
Glycerol	50% (v/v)	30% (v/v)	20% (v/v)
Tris base	-	-	100 mM, pH 6.8
SDS	-	-	4.0% (w/v)

Question: Where do xylene cyanole (XC) and bromophenol blue (BPB) dyes migrate in agarose gel electrophoresis? Where do these two tracking dyes migrate in a polyacrylamide gel?

Answer: Xylene cyanole (XC) and bromophenol blue (BPB) are tracking dyes for gel electrophoresis. According to either "Maniatis" (Sambrook, Fritsch & Maniatis (1989) Molecular Cloning, A laboratory Manual; 2nd Edition., CSHL Press) or FMC, the dyes migrate as follows:

i). Migration in a polyacrylamide gel:

Acrylamide (% [w/v])	XC (base pairs)	BPB (base pairs)
3.5	460	100
5.0	260	65
8.0	160	45
12.0	70	20
15.0	60	15
18.0	45	12

ii). Migration in a denaturing polyacrylamide gel:

% Acrylamide/Urea	XC (base pairs)	BPB (base pairs)
4	155	30
6	110	25
8	75	20
10	55	10

iii). Migration in an agarose gel (Source: FMC):

% Agarose	1X TAE Buffer		1X TBE Buffer
	XC	BPB	XC	BPB
0.30%	24,800	2,900	19,400	2,850
0.50%	11,000	1,650	12,000	1,350
0.75%	10,200	1,000	9,200	720
1.00%	6,100	500	4,100	400
1.25%	3,560	370	2,500	260
1.50%	2,800	300	1,800	200
1.75%	1,800	200	1,100	110
2.00%	1,300	150	850	70

Question: What is the formulation of your RNA Gel Buffer (10X MOPS Buffer)?

Answer: The formulation is provided in a Technical Information sheet available from Customer Service. Alternatively, it may be viewed on-line.

Click on TIS to access the library of Technical Information Sheets for more information.

Question: Why do you not put formamide in your gel loading solutions?

Answer: Formamide, an organic denaturant, is commonly used in nucleic acid applications such as sequencing. It is well known that formamide, even at very low temperatures (e.g., –20 ° C), will break down into formic acid and ammonia. Both by-products are capable of degrading RNA and DNA. Thus, it is prudent to use freshly deionized formamide before adding it to our DNA Gel Loading Solution and/or to our RNA Gel Loading Solution. Click on TIS to access the library of Technical Information Sheets for more information.

Question: I understand that Quality Biological is in the business of preparing custom agar plates? What is your minimum custom order? What size plates do you use and what are their fill volumes? What is the turn-around time?

Answer: Our agar plates are supplied in two sizes: 15 X 100mm (standard) and 15 X 150mm. Our minimum requirement is 100 plates. You may specify a fill volume; we typically do 25 and 40mL fills. In most cases, we can deliver a custom order within 5-10 business days.

Question: Why are your cubitainers of molecular solutions/buffers not guaranteed sterile and absent of DNases and RNases?

Answer: For reagents/solutions that are capable of being tested for sterility and for the absence of DNases and RNases, we can deliver such quality assurances to the customer. On the other hand, our cubitainer suppliers cannot guarantee sterility nor the absences of nucleases. Thus, once the quality assured product is added to a non-quality assured container (e.g., cubitainer), we can no longer guarantee sterility, etc., of the finished goods.