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				<title>CEM Corporation : FAQ.</title>
				<link>http://www.cem.com/</link>
				<description>CEM Corporation, a private company based in Matthews, North Carolina, is the leading provider of microwave laboratory instrumentation. The Company has subsidiaries in the United Kingdom, Germany, Italy and France, as well as a global network of distributors. CEM designs and manufactures systems for life sciences, synthetic chemistry, analytical chemistry, and processing plants worldwide. The Company's products are used in many industries including pharmaceutical, biotech, chemical, environmental, and food processing, as well as for academic research.</description>

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				<copyright>All content Copyright 2009 CEM Corporation<a href="{e_PLUGIN}content/content.php?content.12">CEM is an official GSA Supplier</a> | <a href="http://cem.com/pdf/94160f CEMCorp.pdf">ISO certification since 1994</a> | <a href="{e_BASE}page97.html">Privacy Policy</a> | <a href="{e_PLUGIN}rss_menu/rss.php">RSS Feeds</a></copyright>
				<managingEditor>rich.davis@nospam.com (Admin)</managingEditor>
				<webMaster>rich.davis@nospam.com (Admin)</webMaster>
				<pubDate>Thu, 09 Sep 2010 03:19:11 -0600</pubDate>
				<lastBuildDate>Thu, 09 Sep 2010 03:19:11 -0600</lastBuildDate>
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						<title>Does the system require a vacuum pump?</title>
<link>http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16.182</link>
<description><![CDATA[No, the Liberty1 only needs a source of nitrogen or argon gas.]]></description>
<category domain='http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16'>Liberty1 FAQs</category>
<author>noauthor@nospam.com (Grace)</author>
<pubDate>Tue, 05 Jan 2010 07:50:54 -0700</pubDate>
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						<title>Is the microwave safe?</title>
<link>http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16.181</link>
<description><![CDATA[The Discover microwave cavity used with the Liberty1 is a very safe system. It undergoes strict safety guidelines and is ensured for the following:a. Microwave leakage All Discover microwave systems are tested to leak less than 1mW/ cm2. A domestic microwave can leak about 5 mW/cm2 of power. The Discover contains 2-independent physical interlock systems as well as 1-independent digital interlock to completely shut off the microwave power if the cavity is opened.b. Explosion Proof - It is designed to be explosion proof for pressurized reactions up to 300°C and 300 PSI that are used with organic synthesis. In peptide synthesis, reactions are not pressurized and maximum temperatures are around 75-80 °C.]]></description>
<category domain='http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16'>Liberty1 FAQs</category>
<author>noauthor@nospam.com (Grace)</author>
<pubDate>Tue, 05 Jan 2010 07:49:56 -0700</pubDate>
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						<title>Is racemization a concern in microwave SPPS?</title>
<link>http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16.180</link>
<description><![CDATA[Cysteine and histidine can show elevated levels of racemization at higher temperatures. Controlled microwave methods at 50°C have been developed for these amino acids that minimize this potential side reaction, while the other 18 standard amino acids are coupled at 75°C. During activation, the ester form of the amino acids results in a slightly more acidic proton on the a-carbon. For cysteine, the electron-withdrawing effect of the sulfur atom on the side chain further stabilizes removal of the proton. Histidine contains a p-nitrogen on its side chain that can directly remove the a-carbon during activation.Once coupled, both of these amino acids do not show the ability to racemize at 80°C. Microwave should be controlled during the coupling of these two amino acids, but once coupled, racemization is not an issue at 80°C coupling of subsequent amino acids. In extreme cases these amino acids can be coupled conventionally, while the rest of the peptide is assembled with microwave with no increased risk of racemization.1,2 In the Liberty software this can be set to run automatically each time these amino acids are encountered without user intervention.For further information see:1. Limiting racemization and aspartimide formation in microwave-enhanced Fmoc solid phase peptide synthesis; J. Pept. Sci. 2007, 13, 143-148.2. Solid Phase Peptide Synthesis under Microwave; Chapter 20; Microwaves in Organic Synthesis, Wiley-VCH, Weinheim 2006.3. Microwave-Assisted Solid-Phase Peptide Synthesis on CLEAR Supports; K. Darlak et al.; Poster Presentation at the 19th American Peptide Symposium; San Diego, CA 2005.4. Rapid Microwave-Assisted Solid Phase Peptide Synthesis; M. Erdelyi, A. Gogoll; Synthesis 2002, 11, 1592.]]></description>
<category domain='http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16'>Liberty1 FAQs</category>
<author>noauthor@nospam.com (Grace)</author>
<pubDate>Tue, 05 Jan 2010 07:48:20 -0700</pubDate>
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						<title>Is aspartimide formation a concern during microwave SPPS?</title>
<link>http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16.179</link>
<description><![CDATA[Aspartimide formation can occur under microwave conditions similar to conventional SPPS. With peptides containing "Asp-Gly" segments this can be of particular concern, but also in certain other combinations. It is recommended to use 0.1M HOBt in piperidine based Fmoc deprotection solutions as a preventative measure.Alternatively, in microwave SPPS piperazine can be effectively substituted for piperidine. Piperazine is a non-controlled substance that is not as toxic as piperidine and results in largely decreased aspartimide formation. Piperazine is approximately 3-times slower at removing the Fmoc group and may not be suitable for conventional synthesis, but is very effective with a 3-minute microwave deprotection.For further information see:1. Limiting racemization and aspartimide formation in microwave-enhanced Fmoc solid phase peptide synthesis; J. Pept. Sci. 2007, 13, 143-148.2. Solid Phase Peptide Synthesis under Microwave; Chapter 20; Microwaves in Organic Synthesis, Wiley-VCH, Weinheim 2006.3. Base induced side reactions in Fmoc solid-phase peptide synthesis: Minimization by use of piperazine as N-a-deprotection reagent; Lett. Pept. Sci. 2006, 7, 107-112 .]]></description>
<category domain='http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16'>Liberty1 FAQs</category>
<author>noauthor@nospam.com (Grace)</author>
<pubDate>Tue, 05 Jan 2010 07:45:58 -0700</pubDate>
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						<title>What are the reagent ports on the Liberty1?</title>
<link>http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16.178</link>
<description><![CDATA[There are up to 25 total reagent ports on the Liberty:20 - Amino Acid Bottles, either 125 or 250 mL capacity1 - DMF Port (4L, 8L, 20L, or larger capacity)1 - Deprotection Base1 - Activator1 - Activator Base1 - Capping (Optional)]]></description>
<category domain='http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16'>Liberty1 FAQs</category>
<author>noauthor@nospam.com (Grace)</author>
<pubDate>Tue, 05 Jan 2010 07:42:13 -0700</pubDate>
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						<title>What are the sample loop sizes used on the Liberty1?</title>
<link>http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16.177</link>
<description><![CDATA[The Liberty1 uses the following sample loop sizes:Amino Acids (all 25 positions): 1.25 mLActivator: 1.0 mL, 2.0 mLActivator Base: 0.5 mL, 1.0 mL ]]></description>
<category domain='http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16'>Liberty1 FAQs</category>
<author>noauthor@nospam.com (Grace)</author>
<pubDate>Tue, 05 Jan 2010 07:40:16 -0700</pubDate>
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						<title>What size reaction vessels come standard with the system?</title>
<link>http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16.176</link>
<description><![CDATA[The Liberty1 comes standard with a 30 mL vessel for 0.10 to 0.50mmol scale range, and a 125mL vessel for 0.50-5mmol scale range.]]></description>
<category domain='http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16'>Liberty1 FAQs</category>
<author>noauthor@nospam.com (Grace)</author>
<pubDate>Tue, 05 Jan 2010 07:39:20 -0700</pubDate>
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						<title>How does microwave enhance peptide synthesis?</title>
<link>http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16.175</link>
<description><![CDATA[While certain peptide sequences could be synthesized relatively easily it was noticed early on that other sequences were much more difficult. During chain assembly sudden decreases in reaction rates were observed. In some cases repeated or prolonged reaction time showed no improvement in chain assembly. Optimal reaction conditions require a fully solvated peptide-polymer matrix that allows for efficient reagent penetration. It has been observed that during the synthesis of a difficult peptide the reaction matrix becomes partially inaccessible, typically during the 6-12th residue of the chain. This is thought to occur due to secondary structures of aggregates that result in poor solvation of the peptide-polymer matrix. As a peptide chain is built stepwise on a resin bead it can form aggregates either with itself or neighboring chains. This involves inter or intramolecular hydrogen bonding of the peptide backbone that leads to b-sheet formation.In peptides, the N-terminus amine group and peptide backbone are polar which makes them constantly try to align with the alternating electric field of the microwave. During peptide synthesis this can help break up chain aggregation due to intra and interchain association and allow for easier access to the growing end of the chain. One must also consider the solvent used for SPPS. Both DMF and NMP are medium absorbers of microwave energy, while DCM is a lower absorber. The dielectric loss for NMP, DMF, and DCM are 8.855, 6.070, and 0.382 respectively. Conventional heating relies on energy to migrate in from the outside of the vessel and is a slow and non-specific transfer. Whereas with microwave, energy transfer occurs in 10-9 sec with each cycle of electromagnetic energy. The kinetic molecular relaxation from this energy is approximately 10-5 sec. Thus a large amount of energy can be applied directly to the molecules involved in the reaction in a very efficient manner.Since the successful synthesis of a peptide necessitates near 100 percent completion of two reactions per cycle, microwave energy represents an efficient way to drive these reactions to completion. Common problems in SPPS, typically from aggregation, necessitate a great deal of time and reagent cost to drive to completion. Microwave energy represents a fast and efficient alternative that is useful for providing efficient energy to accelerate both the deprotection and coupling steps.For more information: Click Here]]></description>
<category domain='http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16'>Liberty1 FAQs</category>
<author>noauthor@nospam.com (Grace)</author>
<pubDate>Tue, 05 Jan 2010 07:37:29 -0700</pubDate>
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						<title>What happens if the system runs out of a reagent?</title>
<link>http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16.174</link>
<description><![CDATA[Every reagent line is sensor monitored. If any reagent becomes empty, the system will detect it and pause the synthesis. It will then walk the user through replacing the reagent properly before continuing the synthesis. Additionally, the system waste is monitored and will pause the system if it gets full.]]></description>
<category domain='http://www.cem.com/e107_plugins/faq/faq.php?0.cat.16'>Liberty1 FAQs</category>
<author>noauthor@nospam.com (Grace)</author>
<pubDate>Tue, 05 Jan 2010 07:33:14 -0700</pubDate>
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