h*w
发帖数: 134 | 1 其实optics alignment 不太难，只要你找到calibration的方法。我最讨厌那个脉冲延
时，每次要重合他们，我都要上low coherence spectrometer 去验证。
哪位有简单的办法？ |
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v*****s
发帖数: 20290 | 2 time domain的overlap一般是用非线性的方法去找的。根据光的波长不同，可以使用不
同的Nonlinear powder或者crystal，然后找合频信号。
low coherence spectrometer是什么东西？没听说过啊。 |
|
s****n
发帖数: 234 | 3 This is how we make home-made Halo-Atto647N in our lab using amine/NHS ester
chemistry. It is probably not the most cost-efficient way, but we did get
huge amount of Halo-Atto647N. Hope this would help.
Reagents and Reaction Set Up:
Dissolve 5mg of Atto NHS ester in 400ul of Anhydrous N,N DMF. (Final
Concentration 10mM)
Add 120 ul of 100mM stock solution of Amino HaloTag Ligand. (Final
Concentration 20mM)
Add 3.1 ul of DIPEA (reagent grade) to the solution. (Final Concentration
30mM)
Bring final... 阅读全帖 |
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h**********r
发帖数: 671 | 4 You can scan the OD of the culture by using UV-Vis spectrometer, and then
pick up the wavelength at peak. Determine the CDW (cell dry weight) Vs. OD
at selected wavelength, and make a curve.
For some microbes, it's different. For some green microalgae, some one uses
OD770. For cyanobacteria, people use OD750 or OD730. For some orange conidia
from the fungus, OD420 is used.
|
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s******a
发帖数: 252 | 5 The golden age of metabolism is coming again.
The signaling roles of metabolites have been unappreciated for too long,
even prominent examples like cAMP are everywhere.
Stability and low concentration limit the study of many of them. We may know
less than half of metabolites in our body right now.
High resolution mass spectrometers and systems biology will power the next
wave of discoveries. The fist half of 20th century was the first golden age.
Pasted below are Nobel prizes related to metaboli... 阅读全帖 |
|
s******a
发帖数: 252 | 6 The golden age of metabolism is coming again.
The signaling roles of metabolites have been unappreciated for too long,
even prominent examples like cAMP are everywhere.
Stability and low concentration limit the study of many of them. We may know
less than half of metabolites in our body right now.
High resolution mass spectrometers and systems biology will power the next
wave of discoveries. The fist half of 20th century was the first golden age.
Pasted below are Nobel prizes related to metaboli... 阅读全帖 |
|
b*****s
发帖数: 18 | 7 【 以下文字转载自 Chemistry 讨论区 】
发信人: bigjobs (jobs), 信区: Chemistry
标 题: 内推LC-MS相关职位
发信站: BBS 未名空间站 (Tue Dec 2 00:51:20 2014, 美东)
大家找，想找LC-MS相关职位的同学请看过来，可以帮忙内推。下面是Thermo Fisher公
司的一些职位信息，如果有工业界工作经验最好，没有的话博后经验也可以试试。大家
也可以自己上公司网站看看，如果有别的职位适合你的背景，请发站内信联系，可以内
推。
Product Marketing Specialist, Biopharma Market
in US - California - San Jose, US - New Jersey - Somerset, US -
Massachusetts - Cambridge
Job Description
Position Summary:
The Product Marketing Specialist is expected to be the expert in regards t... 阅读全帖 |
|
s*****5
发帖数: 52 | 8 前辈说的precison/accuracy指的应该是LC-MS定量方法的吧，FDR不会影响这个，特定
到每一个肽或者蛋白也不会有太大影响。而且，不好的spectrum variation都比较大，
一般会被排除。
但是，我觉得FDR会影响整体数据的precision/accuracy.这升高的3%FDR，意味着整个
的score cutoff提高了很多，多的不只是200个蛋白，还有上千的肽和可能上万的PSM.
3%的protein FDR的提升几乎等同于多加了>10% 的PSM，假设一个run有8w个spectrum,
包含进来的质量不好的PSM可能大几千。我们现在定量是base on Peak AUC, 所以这些
低质量的spectrum对整体的定量都会有影响。假设我们spike in了几十个蛋白在背景样
品里，那么这个population的precision可以用coefficient of variation from
median来表示，accuracy用deviation of median from true ratio来表示的话， 这些
低质量的PSM肯定会导致整体数据q... 阅读全帖 |
|
s*****5
发帖数: 52 | 9 前辈说的precison/accuracy指的应该是LC-MS定量方法的吧，FDR不会影响这个，特定
到每一个肽或者蛋白也不会有太大影响。而且，不好的spectrum variation都比较大，
一般会被排除。
但是，我觉得FDR会影响整体数据的precision/accuracy.这升高的3%FDR，意味着整个
的score cutoff提高了很多，多的不只是200个蛋白，还有上千的肽和可能上万的PSM.
3%的protein FDR的提升几乎等同于多加了>10% 的PSM，假设一个run有8w个spectrum,
包含进来的质量不好的PSM可能大几千。我们现在定量是base on Peak AUC, 所以这些
低质量的spectrum对整体的定量都会有影响。假设我们spike in了几十个蛋白在背景样
品里，那么这个population的precision可以用coefficient of variation from
median来表示，accuracy用deviation of median from true ratio来表示的话， 这些
低质量的PSM肯定会导致整体数据q... 阅读全帖 |
|
k****o
发帖数: 728 | 10 谁熟悉Waters Q TOF质谱的维护？最近接手一个老仪器Micromass Q-TOF Ultima API
Mass Spectrometer. 最近发现TOF Penning逐渐升高，从最初的3.0 e-7(听说不能超
过3.5e-7），逐渐升到4.5 e-7.如果仪器处于stand by mode，TOF penning能稍微低点
但也是高于3.5e-7。这个值似乎与mass accuracy 有关。发现超过4e-7后，即便是刚
calibrate后很大的protein(40-100 kDa) mass error也能达到8-15 Da（而小protein
还是很准的）。而前段时间TOF Penning正常时就没有这个问题，mass error对100 kDa
的protein error只有4 Da. 另外，Turbo speeds里面TOF Speed那一项在98-100%之间
徘徊，而过去能一直保持在100%。不知道有没有问题。有没有建议怎么tune一下？ |
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a**y
发帖数: 464 | 11 Several postdoc positions are available in the group of Dr. Huiwang Ai at
the University of California, Riverside http://ailab.ucr.edu. The expertise of our lab is on protein engineering and fluorescent redox probes. Recently, our lab has explored new areas, including the biology and toxicology of oxidative stress, imaging of brain activities, and protein/peptide enzyme inhibitors.
We are looking for postdoctoral fellows with the following
expertise:
1. LC-MS/MS based proteomi... 阅读全帖 |
|
B8
发帖数: 92 | 12 The Department of Environmental Sciences and Engineering at Gillings School
of GlobalPublic Health, University of North Carolina at Chapel Hill has a
postdoc opening. We are looking for a self-motivated postdoc to conduct
omics profiling to understand the interactions between the gut microbiome
and diseases/environmental exposures. Our lab has dedicated high-end mass
spectrometers, including Q-Exactive HF Orbitrap and 6550 Q-TOF.
A PhD degree or solid training in analytical chemistry, proteomics... 阅读全帖 |
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t******t
发帖数: 3045 | 13 nothing to worry about unless the spectrometer has a cryogenic probe |
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P**k
发帖数: 75 | 14 I have a crystal which has several void ( mm scale) included. The crystal
itself
is UV transparent down 350 nm.
I want analyze the composition of the void to know if there is some gas or
just vacuum in side.
Could you please give me any suggestion that what kind of method,
spectrometer or others, could be used?
It is OK to destroy the crystal.
thanks! |
|
W*********m
发帖数: 17 | 15 Joural:Nuclear Instruments and Methods in Physics Research Section A:
Accelerators, Spectrometers, Detectors and Associated Equipment
Volume 338, Issues 2-3, 15 January 1994, Pages 560-567
Title: Determination of natural 32P and 33P in rainwater, marine particles
and plankton by low-level beta counting
N.A. Waser, 1, a, A.P. Fleera, T.R. Hammara, K.O. Buesselera and M.P. Bacona
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TJM-473FMY7-1KF&_user=10&_coverDate=01%2F15%2F1994&_rdoc=35& |
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m******i
发帖数: 73 | 16 Two Postdoc positions are available immediately at Department of Environmental Sciences and Engineering, University of North
Carolina at Chapel Hill. We are working on quantitation of carcinogen-
induced DNA adducts and protein biomarkers. The lab is equipped with 3
Triple quadrupole mass spectrometers, 1 ion trap, 1 ICP-MS and 1 Q-TOF. We
also have several HPLC, UPLC and nano-LC systems. The successful candidates
should have hand-on experience on liquid chromatographic techniques and mass
spect |
|
j******0
发帖数: 258 | 17 Title: Measurement of the scattering coefficient, absorption
coefficient and anisotropy with a commerically available UV-Vis-NIR
Spectrometer
Source: Abstracts of papers [0065-7727] Pietrzykowski yr:2006 vol:231 |
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d********y
发帖数: 176 | 18 a.u. > 2 is outside the dynamic range of many spectrometer anyway and so
two
of your spectra are not really meaningful to start with.
the two spectra with weaker absorption are meaningful and do have some
features around 330-400 nm. your baseline is terrible (should be close to
0). Either your control (i assume you used a dual beam uv-vis) is bad, or
like someone said you've lots of scattering which caused light loss. |
|
f**p
发帖数: 792 | 19 你确定你这个吸收光谱不是溶液的? au是你定义的还是 spectrometer 给的? |
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x****h
发帖数: 300 | 20 都是中文文献：
1. SPECTROSCOPY AND SPECTRAL ANALYSIS , volume 25, issue 5 2005 P 792-795
authors:Kang WJ, Liang SX, Jia LH, et al.
title: Determination of trace cadmium in environment water samples by
flame atomic absorption spectrometry using flow injection on-line
preconcentration with double microcolumns
2. SPECTROSCOPY AND SPECTRAL ANALYSIS, volume 26, issue 7, 2006 P 1345-1348
authors: Wang AX, Guo LP, Wu DM
title: Determination of Pb and Cd in environmental water sample by on-
line... 阅读全帖 |
|
L****r
发帖数: 333 | 21 Applied Biosystems 4000 Q TRAP
The 4000 Q TRAP® combines triple quadrupole scan modes with the
advanced features of MDS SCIEX Linear ion trap scans in a single LC/MS/MS
run that identifies, characterizes, and confirms Phase I and II metabolites.
The system includes three sources—an ESI (IonSpray), APCI (Heated
Nebulizer), and NanoSpray—a vacuum pump, and a PC with Analyst 1.4.1
software.
Applied Biosystems 4000
The API 4000 combines a Liquid Chromatography (LC) Mass Spectrometer (MS)
with a... 阅读全帖 |
|
b***e
发帖数: 1008 | 22 Author(s): AGUILERA C, LUDERWALD I
Source: MAKROMOLEKULARE CHEMIE-MACROMOLECULAR CHEMISTRY AND PHYSICS
Volume: 179 Issue: 12 Pages: 2817-2827 Published: 1978
Title: STRUCTURAL INVESTIGATION ON POLYESTERS BY DIRECT DEGRADATION IN MASS-
SPECTROMETER .5. POLYESTERS FROM TEREPHTHALIC ACID AND-OR SUCCINIC ACID AND
HYDROQUINONE
请发至z***[email protected] 或 我可去下载，
非常感谢！ |
|
x****h
发帖数: 300 | 23 是一个residual gas analyzer用来定量分析连续样品气体中几百ppm的NO。
问题时发现在改变NO浓度的时候，MS要过很长时间（~一小时）才能趋于稳定。
不知道这是不是正常，请教可能的问题是什么。
各位MS专家请指点迷津。。。。 |
|
R*******1
发帖数: 6 | 24 Ad Description for BS/MS Sr Associate Scientist
Responsibilities:
• Work within the Analytical Protein Chemistry area to provide
analytical support for novel peptide and protein therapeutics in pre-
clinical and clinical development.
• Primary responsibilities include the identification and
characterization of post-translational modifications in protein therapeutic
candidates, using state of the art separations technology and mass
spectrometry instrumentation, with an emphasis ... 阅读全帖 |
|
y***n
发帖数: 28 | 25 Physical Chemistry Postdoc Research Opportunity at Boston University
Xin Chen’s research group, newly-founded at Boston University, Department
of Chemistry in 2011, is seeking a postdoctoral researcher (or a visiting
scholar) with experience in ultrafast laser spectroscopy and nonlinear
optics. His/her major responsibility would be to set up and carry
experiments using a board-band vibrational sum-frequency spectrometer and
imaging system. Candidates experienced in nonlinear v... 阅读全帖 |
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|
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b******e
发帖数: 362 | 28 能否展开说说，pros/cons compare to other competitors.
我来研究一下怎莫给包子，随后送上。 |
|
q***l
发帖数: 177 | 29 Agilent 8453
这个扫描速度快，样品放在开放环境（不喜要遮光），用的跟普通的检测器不一样（但
忘了叫。。。） |
|
A*******l
发帖数: 67 | 30 我们用Varian比较多
现在用的都是100和300系列
优点是stability, sensitivity,reproducibility
官方的baseline stability是0.0003 abs/hr,我实测到新的机器可以到0.0001abs/hr，
多次重复一致
缺点是维修比较贵，由于典型的double beam设计，旧仪器chopper元件的故障率很高，
基本上两三年要换一次，当然也是因为我们用的assay比较intense，经常7X20的用
一直很想买他家的50/60系列，但是老板不批钱
50/60系列的优点是速度和方便
像楼上讲的Agilent一样，可以开室测试。因为使用功率非常高的Xenon lamp，而不是
普通的UV/vis lamp，所以室内光源对测试基本没影响。而且由于Xenon lamp直接覆盖
190-1200nm，没有通常所见的uv/vis光源切换造成的spike。这个系列使用dual beam设
计，没有chopper元件，所以故障率比较低。缺点是理论上来讲没有double beam的
stability和reproducibility好，但实测几... 阅读全帖 |
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A*******l
发帖数: 67 | 31 Varian的还有一个优点就是可以自定义扫描精度，调节扫描时间。最快的模式下可以在
3秒内从200到1100
当然如果做high-throughput的话，就另当别论了，肯定比不上用96 plate的 |
|
b******e
发帖数: 362 | 32 多谢，包子已发。
刚查了一下Varian is part of Agilent now. 我们需要一台full spectral scan 和
high dynamic range 兼顾的。
不知PDA/CCD based 和这种传统的monochromator 的比有何优劣？ |
|
s**********e
发帖数: 601 | 33 我们在用的是varian CARY 500 的，我竟然看到隔壁一个教授新买了CARY 5000， 应该
是很先进吧。 |
|
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A*******l
发帖数: 67 | 35 位数相同的是数越大型号越新，功能差不多。
位数越大的，功能越强。 |
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A*******l
发帖数: 67 | 36 是有一段时间了
Agilent自身品牌的UV还没见有人用过，估计并了Varian之后也就不做了吧
monochromator见过一台，描扫的那叫一个慢
不知道你预算有多少？不太多的话50/60就不错，high dynamic肯定能满足
100/300其实dynamic还不如50/60的 |
|
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A*******l
发帖数: 67 | 38 刚去官网查了一下，没见到500，是什么时候的产品啊？ |
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b******e
发帖数: 362 | 39 难道Cary 系列不都是monochromator的？
那scan的又是什摸东西？
60 用的是flashlamp, 个人感觉还是DT要好些。 |
|
A*******l
发帖数: 67 | 40 我觉得你说的monochromator是那种specific single wavelength light input device
.我见到的那台是single channel light emitter，连接别的detector 和sample
chamber用作fluorometer
很少有人把UV/vis叫monochromator吧，虽然原理上它包括某种monochromator作为光源。
Xenon flash lamp 和DT就看个人爱好。DT比较传统，但是除非你买5000/6000系列，不
然我觉得performance差不多。 |
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w**********g
发帖数: 687 | 43 I just put an order through them and it is on the way to be here. Agilent is
kind of too expensive and JACSO is reasonable and reliable too. The software is
more fancy after they demonstrating to my students. |
|
y*****s
发帖数: 1047 | 44 广告都多得很
Posted/Revised: 5/2/2012
Company/Institute: Pfizer Inc
Department:
Position: 2 Year Postdoctoral Fellow – Protein Quantitation in Tissues
by Mass Spectr
Job Location: Andover, MA United States
Description: 2 year Postdoctoral Fellow – Protein Quantitation in
Tissues by Mass Spectrometry and Immunoanalytical Techniques A Postdoctoral
Fellowship is available in Pfizer’s Pharmacokinetics Dynamics and
Metabolism New Biological Entities (PDM-NBE) in Andover, MA. The PDM ... 阅读全帖 |
|
b*******g
发帖数: 1309 | 45 90s‘那个时候PE把AB买了，API是那个时候的产品（？？）
后来的PE又分成了分析部门跟life science，
PE分析部门专门做ICP，AAS之类，后来被其他公司买了，继续用PE的牌子
life science 又变成了AB，然后又分成了做mass spectrometer跟DNA sequence两个公司
现在的PE，2010年才开始做LC-MS，已经不是那个时候的PE了，跟API系列没有关系 |
|
h*******o
发帖数: 1114 | 46 麻烦问问用过下面这个的，Bruker Hyperion 3000 Infrared Microscope attached to
a Bruker Tensor 27 FTIR spectrometer,用了很多液氮了，还是不行，是不是不能开
着程序加液氮降温啊？
肿么办？
谢谢！ |
|
A**********n
发帖数: 824 | 47 感谢楼上几位。
作为一个有效的分析手段，滴定应该在我的考虑之列。由于hydrogen peroxide在水中
并不稳定，样品形成后必须立刻滴定，这对实验过程有很大的制约。可以考虑加入过量
还原剂进行反滴定，这样的话，事实上，走向了探讨hydrogen peroxide分析方法的方
向，我不是在研究分析方法。我是在寻找一种成熟可靠的分析方法，然后用之。
ASTM的仪器分析很好，但是需要fluorometer。哪位知道用spectrometer可进行分析的
方法？
市场上有kit出售，但是我联系过这个厂家，这个kit不能用来分析测量水中的hydrogen
peroxide。http://www.cellbiolabs.com/hydrogen-peroxide-assay 哪位知道有类似的kit出售，并且这个kit可以用来分析测量水中的hydrogen peroxide？ |
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d********y
发帖数: 176 | 48 好像以前也在这里也回答过你的光谱学问题。
透射光 should refer to the forward-traveling laser excitation. so it is not
Rayleigh scattering.
if you only worry about 透射光, then a 90 degree or a back scattering (which
most modern commercial instruments use) doesn't have this problem because
by definition 透射光 doesn't go to the detector.
but if you worry about Rayleigh, regardless what geometry is used (back
scattering, forward scattering, 90
degree), the Rayleigh scattering is usually many many times stronger than
the Raman ... 阅读全帖 |
|
b*****s
发帖数: 18 | 49 大家找，想找LC-MS相关职位的同学请看过来，可以帮忙内推。下面是Thermo Fisher公
司的一些职位信息，如果有工业界工作经验最好，没有的话博后经验也可以试试。大家
也可以自己上公司网站看看，如果有别的职位适合你的背景，请发站内信联系，可以内
推。
Product Marketing Specialist, Biopharma Market
in US - California - San Jose, US - New Jersey - Somerset, US -
Massachusetts - Cambridge
Job Description
Position Summary:
The Product Marketing Specialist is expected to be the expert in regards to
Thermo Fisher Scientific LC-MS products and workflows for the Biopharma
market. Will translate instrument and software perf... 阅读全帖 |
|
h***o
发帖数: 350 | 50 Real-time detection of chemical warfare agent simulants in forensic samples
using active capillary plasma ionization with benchtop and field-deployable
mass spectrometers
Morphy Dumlao, Pablo Martinez-Lozano Sinues, Maryia Nudnova and Renato
Zenobi
Anal. Methods, 2014,6, 3604-3609
DOI: 10.1039/C4AY00303A
Link:
http://pubs.rsc.org/en/Content/ArticleLanding/2014/AY/C4AY00303
Thank you very much. |
|
