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Three-dimensional models, or pharmacophores, describing Euclidean constraints on the location on small molecules of functional
groups (like hydrophobic groups, hydrogen acceptors and donors, etc.), are often used in drug design to describe the medicinal
activity of potential drugs (or ‘ligands’). This medicinal activity is produced by interaction of the functional groups on
the ligand with a binding site on a target protein. In identifying structure-activity relations of this kind there are three
principal issues: (1) It is often difficult to “align” the ligands in order to identify common structural properties that
may be responsible for activity; (2) Ligands in solution can adopt different shapes (or `conformations’) arising from torsional
rotations about bonds. The 3-D molecular substructure is typically sought on one or more low-energy conformers; and (3) Pharmacophore
models must, ideally, predict medicinal activity on some quantitative scale. It has been shown that the logical representation
adopted by Inductive Logic Programming (ILP) naturally resolves many of the difficulties associated with the alignment and
multi-conformation issues. However, the predictions of models constructed by ILP have hitherto only been nominal, predicting
medicinal activity to be present or absent. In this paper, we investigate the construction of two kinds of quantitative pharmacophoric
models with ILP: (a) Models that predict the probability that a ligand is “active”; and (b) Models that predict the actual
medicinal activity of a ligand. Quantitative predictions are obtained by the utilising the following statistical procedures
as background knowledge: logistic regression and naive Bayes, for probability prediction; linear and kernel regression, for
activity prediction. The multi-conformation issue and, more generally, the relational representation used by ILP results in
some special difficulties in the use of any statistical procedure. We present the principal issues and some solutions. Specifically,
using data on the inhibition of the protease Thermolysin, we demonstrate that it is possible for an ILP program to construct
good quantitative structure-activity models. We also comment on the relationship of this work to other recent developments
in statistical relational learning.
Editors: Tamás Horváth and Akihiro Yamamoto 相似文献
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艾冬生 《太赫兹科学与电子信息学报》2003,1(3):14-18
在编制遥测数据处理软件的过程中,面对大量的测试数据,经常需要编写高效率的数据过滤器。本文讨论了一种通过采用跨单元、跨类访问Delphi类的私有域的方法实现快速删除TList批连续结点的新算法,并通过测试结果得到验证。 相似文献
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分别利用Ga2O3粉末和Ga2O3凝胶作为Ga源,采用NH3为N源,在950℃下,分别将两种反应物与流动的NH3反应20 min合成了GaN微晶。用X射线衍射(XRD)、扫描电子显微镜(SEM)、选择区电子衍射(SAED)对微晶进行结构、形貌的分析,特别是对两种不同途径合成GaN微晶的XRD进行了分析比较。结果表明,当Ga源温度为950℃时两种不同的合成途径均可得到六方纤锌矿结构的GaN单晶颗粒,在氮化温度为850℃和900℃时,利用Ga2O3粉末作为Ga源,仅有少量的Ga2O3转变为GaN;而采用Ga2O3凝胶作为Ga源,在相同的温度下,大部分凝胶经过高温氨化反应均可转化为GaN。 相似文献
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AI Quintero Del Río 《Canadian Metallurgical Quarterly》1997,89(1-3):12-14
Motor vehicle accidents are the main cause of death and disability between 1 and 4 years of age. Since 1980 the Academy of Pediatrics has been promoting the correct use of car seats. The major reason that car seats are not fulfilling their full potential is their incorrect or lack of use. In order to evaluate parental knowledge about car seat use for children and their actual use in the population visiting HURRA, a survey was performed which demonstrated that only 57.6% of the parents interviewed had infant car seats and that only 83.3% of owners actually use it. As many as 94.4% had correct knowledge about car seat use, but the majority of correct information was not provided by the medical staff. The majority of parents use seat belts for their own protection but a significantly smaller percentage use car seats for their own children. 相似文献
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Richard Ross 《Information Systems Management》1994,11(3):41-50
Management of distributed environments requires corporate IS managers to shift from being operators of a central utility to facilitators who can recognize the synergy among loosely related groups of users. Success depends on the development of new ways of visualizing and measuring the service delivery process. 相似文献
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Protein analysis of human von Ebner saliva and a method for its collection from the foliate papillae
The lingual serous glands of von Ebner are located close to the foliate and circumvallate papillae. Saliva secreted by these glands provides the immediate environment of the taste buds, and it has been hypothesized that it modulates taste perception. The purpose of this study was to develop a technique for collection of unstimulated and stimulated saliva from human von Ebner glands. Saliva was collected under resting conditions and after application of various gustatory stimuli (sweet, sour, salt, and bitter) by insertion of periostrips into the folds of the foliate papillae of healthy human volunteers. Stimulated saliva was also collected in glass microcapillaries or micropipettes. The flow-rates of unstimulated von Ebner saliva were 2.3 +/- 0.6 (S.E.) microL/min and 4.5 +/- 1.2 (S.E.) microL/min with 1% citric acid stimulation. The protein content was 2.5 +/- 0.5 (S.E.) mg/mL. The SDS gel electrophoretic profile of von Ebner saliva revealed two protein bands of Mr 18,000 that were identified on Western blots as von Ebner gland (VEG) proteins. Although lingual lipase activity was detected at very low levels by enzyme assay, this protein was not detected on Western blots. This collection technique should prove useful for analysis of specific functions associated with secretion from von Ebner glands. 相似文献