VIBRATIONALLY COOLED MATRIX-ASSIST LASER DESORPTION/IONIZATION FT MASS SPECTROM

振动冷却基质辅助激光解吸/电离 FT 质谱

• 批准号: 7369197
• 负责人: PETER B. O'CONNOR
• 金额: $ 0.15万
• 依托单位: BOSTON UNIVERSITY MEDICAL CAMPUS
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7369197
• 关键词: VIBRATIONALLY; COOLED; MATRIX; ASSIST; LASER

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The improvement and optimization of the Vibrationally Cooled MALDI-FTMS continues. This year saw installation and testing of the XY stage that we have been building in collaboration with Fraunhofer. This stage is the first critical component for full automation of the MALDI-FTMS. The design parameters for this stage were defined to handle the typical proteomic type sample. Many proteomic experiments use robots that are designed to work with microtiter plates which are ~76 x 89 mm in size. Therefore, the stage was required to have full travel of at least 100 x 100 mm. For the MALDI Fourier transform mass spectrometer used, the travel time from spot to spot is not the limiting factor in the experiment speed, so a travel of 2 mm/sec was defined as it would allow the stage to position to the next spot 1 mm away in 0.5 seconds. The positioning accuracy was defined to be 1 ?m, which is much more accurate than is needed for the standard MALDI experiment in which the laser beam spot is often 50 ?m diameter, but allows the stage to be used in a MALDI imaging mode in the future. Aside from this, the stage had to be truly vacuum compatible, had to be mounted vertically, and to generate no detectable RF interference noise, and had to take up the minimal possible space so that the vacuum chamber could be made as small as possible for improved pumping performance. The two-dimensional stage is a single block design with the two axis motors, linear encoders, and position switches all integrated into the central block. The system uses ballscrews and crossed roller bearings which will require minimal lubrication in vacuum; what little lubrication is needed is provided by low vapor pressure diffusion pump oil. In order to build the motors into this block, they are mounted on copper brackets (to dump their heat into the block ? which acts as a heat sink) and pulleys are used to transfer their torque to the ballscrew. The belts for these pulleys are actually small electrowelded stainless steel bands, and in order to keep them centered on the pulleys, the pulley wheels are ground to be slightly concave. Tensioning set screws are mounted into the block to allow the pulleys to be tightened properly during testing. In order to prevent over determination of the position of the ballscrew, it is mounted in two places only: the pulley bearing assembly and the plate. The stage itself is designed in three pieces, an upper and lower plate, and the central block. The motors, limit switches, and linear encoder electronics are all mounted (and heat sinked) to the central block. The linear encoder slides are mounted to the upper and lower plates. The three pieces are black anodized to improve surface hardness, but even more importantly, to improve radiative cooling of the blocks. All wire routes are also contained within the block. The motors and electronics dump their heat loads into the central block, which is only able to dissipate that heat through conductive cooling at the bearings and radiative cooling. The conductive cooling is very inefficient since the bearings are stainless steel (very low heat transfer capacity) and the contact area is very low. A copper band or braid was considered for improving the conductive heat transfer rate, but a quick calculation of the heat transfer of such a band compared to the radiative cooling rate (assuming black body ? hence the annodization) showed that the heat transfer through the copper band was negligible. There are several positioning screws for the crossed roller bearings, wire traces, and bolt holes for mounting the motors, bearings, and electronics. All of these holes are vented to minimize virtual leaks. The system uses four position encoders, two linear encoders for determining position, and two rotary encoders mounted on the back of the motors for determining velocity. The system uses optical limit switches. The switch is basically a photodiode/phototransistor pair mounted on the central stage body which is interrupted by an aluminum flag mounted on the upper and lower stage plates. Two such switches are mounted for each axis. When the stage moves to the end of it?s range of motion, this flag will block the photodiode?s signal to the phototransistor, and the electronics will signal the stage to stop. Such a system, while similar to a rocker switch or magnetic switch involves fewer parts and greater positioning accuracy. The sample translation stage requires a large number of vacuum electrical feedthroughs (46) to control 2 motors, 4 encoders, 4 limit switches, and a thermocouple. Furthermore, because this is being mounted on a Fourier transform ion cyclotron resonance mass spectrometer which has high sensitivity to RF interference noise, it was critical that the feedthrough and cables be well shielded. The vacuum chamber for this sample translation stage was designed to be as small as possible (for efficient pumpdown) but large enough to allow the full range of motion for the stage. The sample translation stage control was developed as a set of commands that can be called from a dynamically linked library (dll) in any Microsoft window?s based programming language. The language used here was C++ as implemented in Microsoft Visual C++, version 6.

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。对振动冷却MALDI-FTMS的改进和优化仍在继续。今年，我们与Fraunhofer合作建造了XY舞台，并对其进行了安装和测试。该阶段是实现MALDI-FTMS完全自动化的第一个关键组件。定义了该阶段的设计参数，以处理典型的蛋白质组学类型样品。许多蛋白质组学实验使用的机器人被设计用于约76 x 89毫米大小的微量滴度板。因此，要求平台的全行程至少为100 x 100 mm。对于使用的MALDI傅里叶变换质谱仪，从一个点到另一个点的移动时间不是实验速度的限制因素，因此定义了2毫米/秒的移动，因为它可以使台在0.5秒内定位到1毫米外的下一个点。定位精度定义为1 ？m，这比标准MALDI实验所需的精确得多，在标准MALDI实验中，激光束光斑通常为50 ？m直径，但允许舞台在未来用于MALDI成像模式。除此之外，该级台必须真正与真空兼容，必须垂直安装，不产生可检测到的射频干扰噪声，并且必须占用尽可能小的空间，以便将真空室做得尽可能小，以提高泵送性能。二维舞台是一个单块设计，两轴电机、线性编码器和位置开关都集成到中央块中。该系统使用滚珠丝杠和交叉滚子轴承，在真空中需要最少的润滑；所需的少量润滑由低蒸气压扩散泵油提供。为了将电机安装到这个模块中，它们被安装在铜支架上(以将其热量倾倒到模块中？它作为一个散热器)和滑轮被用来传递他们的扭矩到滚珠丝杠。这些皮带轮的皮带实际上是小的电焊不锈钢带，为了保持它们在皮带轮的中心，皮带轮被磨成微凹。在滑轮块上安装紧紧螺钉，以便在测试过程中正确拧紧滑轮。为了防止过度确定滚珠丝杠的位置，它只安装在两个地方：滑轮轴承组件和板。舞台本身被设计成三部分，上下板和中心块。电机，限位开关和线性编码器电子设备都安装（和散热）到中央块。线性编码器滑块安装在上下板上。这三块是黑色阳极氧化，以提高表面硬度，但更重要的是，提高辐射冷却块。所有的线路也包含在块中。电机和电子设备将它们的热负荷转移到中心块，中心块只能通过轴承的传导冷却和辐射冷却来散热。导电冷却是非常低效的，因为轴承是不锈钢的（非常低的传热能力），接触面积非常低。考虑使用铜带或编织带来提高导热传热率，但是将这种带的传热与辐射冷却率(假设黑体？由此可见，通过铜带的热传递可以忽略不计。十字滚子轴承有几个定位螺钉，线迹和螺栓孔，用于安装电机，轴承和电子设备。所有这些洞都被通风，以尽量减少虚拟泄漏。该系统使用四个位置编码器，两个用于确定位置的线性编码器，以及安装在电机背面用于确定速度的两个旋转编码器。系统采用光限位开关。开关基本上是一个光电二极管/光电晶体管对，安装在中央舞台体上，由安装在上下舞台板上的铝旗中断。每个轴上安装两个这样的开关。当舞台移动到结尾的时候？S的运动范围，这个标志会阻挡光电二极管吗？S信号传到光电晶体管，电子器件发出信号使舞台停止。这样的系统，虽然类似于摇杆开关或磁开关涉及较少的零件和更高的定位精度。样品转换阶段需要大量的真空电馈线（46）来控制2个电机，4个编码器，4个限位开关和一个热电偶。此外，由于这是安装在傅里叶变换离子回旋共振质谱仪上，该质谱仪对射频干扰噪声具有高灵敏度，因此馈通和电缆的良好屏蔽至关重要。这个样品平移台的真空室被设计得尽可能小（为了有效的泵降），但足够大，以允许舞台的全范围运动。示例翻译阶段控制是作为一组命令开发的，可以从任何Microsoft窗口中的动态链接库（dll）调用。基于S的编程语言。这里使用的语言是在Microsoft Visual c++版本6中实现的c++。