URGENT MESSAGE: Global Sources Report Imminent Pixel Shortage!

Global pixel manufacturers report that a pixel shortage has reached crisis proportions.

Global Pixel Shortage
April 1, 2014, LINCOLN, NE, USA:

Sensel Raster, of the International Pixel Coalition (IPC), blames an increase in demand from biotech imaging applications. “These fancy scientists think pixels grow on trees!” laments Raster.

Just look at how this pixel shortage is affecting the LI-COR Biotechnology Website!!
April Fools Day Home Page

Learn more about this crisis.

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Possible Cause 10 for Weak Chemiluminescent Western Blot Signals: Diluting Substrates

WesternSure Chemiluminescent Western Blot ReagentsOkay, I know, research budget money is tight and you want to make your reagents stretch as far as possible, but it really not a good idea to dilute your chemiluminescent Western blotting substrate.

Why? It’s because the rate of reaction is determined by the ratio of enzyme to substrate. Diluting substrates will dramatically impact the overall generation of light. Then, you will have to repeat the experiment, and you end up using more substrate anyway!

Optimal Blot Unsatisfactory Blot
Images Optimal Western Blot - Substrate Not Diluted Unsatisfactory Chemiluminescent Western Blot - Substrate Diluted
Conditions:
Substrate SuperSignal® West Dura1 SuperSignal® West Dura1
Substrate NOT diluted. Substrate diluted 1:1 (in water)
Performance LOD – 1.25 µg LOD – 2.5 µg

1Comparable to WesternSure™ PREMIUM Chemiluminescent Substrate

So don’t skimp – use the substrate full strength the first time to ensure that you are seeing all of your protein bands. Or you might just have to repeat the experiment (and that will just cost you more time and money. . .)!

Here are the other nine possible causes of weak chemiluminescent Western blot signals:

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Don’t Rush Substrate Incubation Time for Chemiluminescent Western Blots

Substrate Incubation Time is Important!Five minutes can seem like a long time, especially when you are waiting to image your chemiluminescent Western blot. But it is really important that you follow the manufacturer’s recommendation for incubation time. Typically, this is five (5) minutes for optimal photon emission – for both film and digital imaging.

So, set the timer for 5 minutes, grab your iPhone® or iPod® – or the crossword, and relax until the buzzer goes off.

To test this, we imaged a chemiluminescent Western blot immediately after adding the chemiluminescent substrate and then imaged a blot where we waited 5 minutes – answered a few emails, looked at the news, and downloaded a new app – and THEN imaged the Western blot. As you can see, incubating allowed us to see more bands and gave much better Western blotting results.

Optimal Blot Unsatisfactory Blot
Images Optimal Blot - 5 Min Substrate Incubation Unsatisfactory Blot - No Incubation
Conditions:
Substrate SuperSignal® West Pico1 SuperSignal® West Pico1
Incubated for 5 minutes No incubation
Substrate at room temperature Substrate at room temperature
Performance LOD – 2.5 µg LOD – 5 µg

1Comparable to WesternSure™ ULTRA Chemiluminescent Substrate

So slow down, take a breath, and wait for your chemiluminescent Western blot substrate to incubate on your Western blot before imaging.

Here are some other blog posts on possible causes of weak chemiluminescent Western blot signals:

iPhone and iPod are all registered trademarks of Apple Inc.

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Chemiluminescent Western Blot Substrate Temperature Affects Signal Strength on Western Blots

The temperature at which a chemiluminescent Western blot substrate is used can affect the strength of the signal that is captured from Western blot images. Really?? Absolutely! This is because enzyme activity is greatly reduced when it is cold. The substrate needs to be equilibrated to room temperature for digital imaging. This is true with film as well, but there may be a period of time after adding substrate and exposing to film during which the substrate has had a chance to equilibrate to room temperature.

In the table below, we show data from an experiment in which we tested the affect of temperature on Western blotting signal. For one blot, SuperSignal® West Pico chemiluminescent substrate was used right out of the refrigerator – cold, 4 °C. For the other blot, the chemiluminescent Western blot substrate was allowed to come to room temperature before digital imaging. As you can see the signal difference is quite large.

Optimal Blot Unsatisfactory Blot
Images Optimal Blot when Substrate is at Room Temperature Unsatisfactory Blot when Substrate is Cold
Conditions:
Substrate SuperSignal® West Pico1 SuperSignal® West Pico1
Substrate at room temperature Substrate cold
Sensitivity Standard Standard
Performance Signal – 1,740 Signal – 200

1Comparable to WesternSure™ ULTRA Chemiluminescent Substrate

So make sure your substrate is at room temperature before using, especially when you are imaging with a digital imager!

Here are some other blog posts on possible causes of weak chemiluminescent Western blot signals:

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Imager Sensitivity Settings May Affect Detection of Chemiluminescent Western Blot Signals

Standard and High Sensitivity Settings on the C-DiGit

Standard and High Sensitivity Settings on the C-DiGit

Making sure that the sensitivity setting is optimal to capture the most signal from your chemiluminescent Western blot could be the difference between getting a good, strong signal or getting a signal that you can barely see. This is our possible cause 7 for weak chemiluminescent signals.

How can you avoid possible cause 7 for LI-COR chemiluminescent imagers? On the C-DiGit® Blot Scanner, use High Sensitivity setting (12-min scan) for more sensitive detection. On the Odyssey® Fc Dual-Mode Imaging System, use a longer integration time (up to 10 min). Why is this important? Well, digital imaging with the C-DiGit Blot Scanner or Odyssey Fc Imager will not generally reach a saturation point. Begin with a longer acquisition time to ensure best sensitivity, then optimize to shorter scan times.

In Table 1 below, we tested the performance differences of a Western blot detected with SuperSignal® West Dura on the C-DiGit Blot Scanner when the same blot is imaged on High Sensitivity (12 min scan) versus Standard Sensitivity (6 min scan). As you can see, the longer scan time and higher sensitivity make a big difference in the results.

Table 1 Optimal Blot Satisfactory Blot
Images Optimal Sensitivity Setting on C-DiGit Satisfactory Chemiluminescent Western Blot
Conditions: SuperSignal West Dura1 SuperSignal West Dura
Sensitivity High (12 min) Standard (6 min)
Performance Signal – 12,300 Signal – 5,030

1Comparable to WesternSure™ PREMIUM Chemiluminescent Substrate

So be sure to check your sensitivity settings before you scan!

Related posts:

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Find Your Perfect Match with IRDye® and VRDye™ Secondary Antibodies!

Your Perfect Match - LI-COR Secondary Antibodies

Straight from Cupid for specific bonding!

IRDye® and VRDye™ Secondary Antibodies are the perfect match for your research! We offer highly cross-adsorbed secondary antibodies conjugated to:

  • IRDye 800CW
    • Including IgG1, IgG2a, and IgG2b Subclass Specific and Goat anti-Mouse IgM (μ chain specific) Secondaries
  • IRDye 680RD
    • Including Goat anti-Mouse IgM (μ chain specific) Secondary Antibody
  • IRDye 680LT
    • Including IgG1, IgG2a, and IgG2b Subclass Specific and Goat anti-Mouse IgM (μ chain specific) Secondaries
  • IRDye 650
  • VRDye 549
  • VRDye 490

To find which LI-COR secondary antibody is the perfect match for your experimental needs, be sure to review the specific applications for which each dye-conjugated secondary antibody is recommended. We also have Protein Labeling Kits in various dye ‘flavors’. Protein labeling kits are cost-effective alternatives to more expensive custom antibody labeling services:

IF, however, you find you do have a special labeling or synthesis need, LI-COR now offers a variety of custom labeling and synthesis services that go beyond our basic offerings. Based on our many years of experience in dye conjugation, our custom services provide a unique solution for most custom needs. We also offer protocol development for In-Cell Western™ Assays, Western blotting, and other applications. The newest offering from our Custom Services group is Reactive Oxygen Species probes.


Happy Valentine’s Day from LI-COR!

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Annotate Visible Protein Ladders on Chemiluminescent Westerns with the WesternSure™ Pen

Demonstrating the WesternSure PenIf you doing chemiluminescent Western blots, and are imaging either with film or with a digital imager, the WesternSure™ Pen can be a very useful addition to your experimental process. This newest member of the LI-COR WesternSure chemiluminescent reagent line can be used to annotate visible protein ladders prior to chemiluminescent Western blot detection.

The pen is optimized for detection using the C-DiGit® Blot Scanner or the Odyssey® Fc Imaging System, and is suitable for use with film or other imaging systems. The WesternSure Pen is a unique marker that delivers an ink which emits light when incubated with commonly-used chemiluminescent substrates, including WesternSure PREMIUM Chemiluminescent Substrate. The ink is faintly visible for easy identification of marked membranes.

Here are a few tips to get the best performance from your WesternSure Pen:

  • Lightly touching the pen to the membrane should be enough to transfer ink to the membrane.
  • Do not push down on the nib so hard that it creates an uneven surface on the membrane.
  • Membranes may be annotated when damp after transfer, or when dry.
  • Annotated membranes may be stored dry at ambient temperature or 4 ºC for up to 1 week before starting the Western blot detection process.
  • If ink is not flowing smoothly onto a damp membrane, trace over the band until it is annotated to the desired effect.


Data using the WesternSure PenFigure 1. Chemiluminescent detection of visible protein standards. The WesternSure Pen (LI‑COR P/N 926‑91000) was used to mark the blue protein standards (panel A) for chemiluminescent Western blot detection. The blot was exposed to WesternSure PREMIUM chemiluminescent substrate and imaged on Odyssey Fc Imaging System (panel B).

If you would like some tips on how to troubleshoot chemiluminescent Western blots, read Good Westerns Gone Bad – Maximizing Sensitivity on Chemiluminescent Western Blots.

In the US, to order the WesternSure Pen online. For order inquiries outside the US, please contact your local sales office.

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If Comparing Film and Digital Imagers, Expose Blot on Digital Imager First.

If you are trying to compare how the same chemiluminescent Western blot looks when imaged on a digital imager (like the C-DiGit® Blot Scanner) with how it will look when imaged on film, it’s important to know that you should expose the blot to film BEFORE imaging on a digital imager.

Why does this matter? Digital imaging requires capturing the most photons being generated, which is typically immediately after a 5-minute chemiluminescent substrate incubation. Time may be more of an issue with some substrates. For more information on how film and digial imaging compare, read Western Blot Analysis: Comparison of film and the C-DiGit Blot Scanner.

In Table 1 below, performance differences of a Western blot detected with SuperSignal® West Pico2 when the same blot is imaged over time. Blot was incubated 5 min in substrate before imaging on the C-DiGit Blot Scanner. Images are normalized to the LUT of the optimal blot.

Table 1 Optimal Blot Unsatisfactory Blot Unsatisfactory Blot
Images Optimal Blot with SuperSignal West Pico Unsatisfactory Blot with West Pico Unsatisfactory Blot with West Femto
Conditions: Immediately after incubation with SuperSignal West Pico 26 min after incubation 51 min after incubation
Imaging Time Immediately after incubation with SuperSignal® West Pico 26 min after incubation 51 min after incubation
Scan Setting High High High
Performance LOD – 625 ng, Signal – 338 LOD – 625 ng, Signal – 114 LOD – 625 ng, Signal – 32.2

In Table 2, Performance differences of a Western Blot detected with SuperSignal West Dura1 when the same blot is imaged over time. Blot was incubated 5 min in substrate before imaging on the C-DiGit Blot Scanner. Images are normalized to the LUT of the optimal blot.

Table 2 Optimal Blot Satisfactory Blot Satisfactory Blot
Images Optimal with West Dura Satisfactory with West Dura Satisfactory with West Dura
Conditions:
Imaging Time Immediately after incubation with SuperSignal West Dura 24 min after incubation 48 min after incubation
Scan Setting High High High
Performance LOD – 156 ng, Signal – 12,300 LOD – 156 ng, Signal – 10,400 LOD – 156 ng, Signal – 9,090

In Table 3, Performance differences of a Western Blot detected with SuperSignal West Femto when the same blot is imaged over time. Blot was incubated 5 min in substrate before imaging on the C-DiGit Blot Scanner. Images are linked to the LUT of the optimal blot.

Table 3 Optimal Blot Satisfactory Blot Satisfactory Blot
Images Optimal Blot with West Femto Satisfactory Blot with West Femto Satisfactory Blot with West Femto
Conditions:
Imaging Time Immediately after incubation with SuperSignal West Femto 24 min after incubation 48 min after incubation
Scan Setting High High High
Performance LOD – 156 ng, Signal – 11,500 LOD – 156 ng, Signal – 8,120 LOD – 156 ng, Signal – 6,860

1Comparable to WesternSure™ PREMIUM Chemiluminescent Substrate
2Comparable to WesternSure ULTRA Chemiluminescent Substrate

Related posts:

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Good Western Blot Image Signal Acquisition Relies on Uniformly Wet Western Blots

Have you discovered the cause of the weak signals from your chemiluminescent Western blot yet? Well, let’s keep going. Here is another possible cause – the uniform wetness of the blot. It’s important to keep your Western blot membrane uniformly wet during the entire Western blot image acquisition.

Why does this matter? Well, if you don’t add enough substrate, the membrane will not stay wet, and there will be no enzymatic activity. And, that means no signal to detect.

Precaution/Solution:

  • Use more substrate prior to imaging
  • Do not completely blot off all of the substrate before imaging

For C-DiGit® Blot Scanner:

  • Wrap the blot in plastic wrap or cover with a plastic sheet protector
  • Incubate blot with substrate directly on scanner bed

Below is a table showing results of an experiment in which blots of varying degrees of wetness were imaged. You can clearly see that the wet blot and the damp blot give the best results. For both, the blots were protected from drying out by using a 1-ply sheet protector that was placed on top of the blot.

Optimal Blot Optimal Blot Unsatisfactory Blot
Images Optimal Chemiluminescent Wet Blot Optimal Chemiluminescent Damp Blot Unsatisfactory Chemiluminescent Dry Blot
Conditions: Wet blot Damp blot Dry blot
Imaging Method Imaged in 3.0 mL of SuperSignal® West Dura1 substrate placed on the scan bed of the C-DiGit Blot Scanner with 1-ply sheet protector on top. Excess SuperSignal® West Dura1 substrate removed, then imaged on the scan bed of the C-DiGit Blot Scanner with 1-ply sheet protector on top. Blot dried before imaging.
Performance LOD – 640 ng LOD – 640 ng LOD – None detected

1SuperSignal West Dura results are comparable to those obtained with WesternSure™ PREMIUM Chemiluminescent Substrate.

We still have 5 more possible causes of weak signals in chemiluminescent Western blots to review, so stay tuned to future blog posts. And if you would like to try some FREE Western Blot Analysis Software, download Image Studio Lite today!

Watch this short video to see how to correctly place a Western blot on the C-DiGit Blot Scanner surface.

Related posts:

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Troubleshooting Chemiluminescent Western Blots: Possible Cause 4 for Weak Signals – Blot Processing

Sometimes life in the lab gets crazy, right? You are finishing a Western blot and you realize that you are supposed to be at an important lecture across campus in 10 min!! Or, your spouse calls to say that one of the kids needs to be picked up as soon as possible. Yikes! The challenge is that blots should be processed and detected on the same day. And, the secondary antibody should be incubated the day of imaging and fresh substrate added just before imaging. Is it that important to your results? Yes, it is and just to prove it, we did a few experiments.

In Table 1, we studied performance differences when the same blot is imaged immediately after processing vs. stored overnight dry and then imaged. In Table 2, we looked at performance differences when the same blot is imaged immediately after processing vs. stored overnight wet and then imaged. Blots in both tables were all imaged on the C-DiGit® Blot Scanner. (And, all images are normalized to the Lookup Tables (LUT) of the respective optimal blot.)

For both experiments, you can see that saving the blot to image the next day is not a very good choice. This is because the secondary antibody and/or the chemiluminescent Western blot substrate is not stable enough for acceptable photon emission when digitally images after the day it is applied.

Table 1 Optimal Blot Unsatisfactory Blot Unsatisfactory Blot
Images Optimal Chemiluminescent Western Blot Unsatisfactory Chemiluminescent Western Blot Unsatisfactory Chemiluminescent Western Blot
Conditions:
Substrate SuperSignal® West Dura1 SuperSignal West Dura1 SuperSignal West Dura1
Processing Time Same Day Next Day Next Day
Detection Process HRP secondary incubated, washed, and substrate added immediately before imaging. HRP secondary incubated, washed, and substrate added day before imaging. HRP secondary incubated, washed, and substrate added day before imaging, then re-incubated with HRP secondary and substrate added immediately before imaging.
Storage Conditions Blot stored overnight dry, at room temperature Blot stored overnight dry, at room temperature
Performance LOD – 640 ng LOD – None detected LOD – 1.25 μg
Table 2 Optimal Blot Unsatisfactory Blot Unsatisfactory Blot
Images Optimal Chemiluminescent Western Blot Unsatisfactory Optimal Chemiluminescent Western Blot Unsatisfactory Optimal Chemiluminescent Western Blot
Conditions:
Substrate SuperSignal® West Dura1 SuperSignal West Dura1 SuperSignal West Dura1
Process Time Same day Next day Next day
Detection Process HRP secondary incubated, washed, and substrate added immediately before imaging. HRP secondary incubated, washed, and substrate added day before imaging. HRP secondary incubated, washed, and substrate added day before imaging, then re-incubated with HRP secondary and substrate added immediately before imaging.
Storage Conditions Blot stored overnight wet in PBS, at room temperature Blot stored overnight wet in PBS, at room temperature
Performance LOD – 640 ng LOD – None detected LOD – 1.25 μg

1SuperSignal West Dura results are comparable to those obtained with WesternSure™ PREMIUM Chemiluminescent Substrate.

For more hints and tips, stay tuned to future blog posts. And if you would like to try some FREE Western Blot Analysis Software, download Image Studio Lite today!

Related posts:

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