Effects of patient-specific positioning guides (PSPGs) vs. conventional instrumentation on patient-reported outcome in total knee arthroplasty: secondary analysis of a randomized controlled trial after 5 years.

BACKGROUND AND PURPOSE: The use of patient-specific positioning guides (PSPGs) in total knee arthroplasty (TKA) has been advocated as a means of improving patient outcomes, but the reception of PSPGs has been mixed. The aim of our study was to compare patient-reported outcomes (KOOS, NRS-11, EQ-5D-3L, EQ-VAS) after TKA using PSPG with conventional instrumentation (CI) to determine whether there is a discernible clinical benefit to using PSPGs. PATIENTS AND METHODS: This multicenter randomized controlled trial (RCT) followed 77 patients who were randomly assigned to 1 of 2 cohorts between September 2011 and January 2014-one receiving TKA with PSPGs (from Materialise NV) and one receiving TKA with CI-with each cohort followed up until 5 years after the operation. The Vanguard Cruciate Retaining Total Knee System and Refobacin Bone Cement R were used in all operations. KOOS was evaluated using confidence intervals, with differences of less than 10 KOOS units between the cohorts interpreted as indicating the absence of a clinically meaningful difference. RESULTS: No significant differences were found in any of the measured clinical outcomes-KOOS, NRS-11, EQ-5D-3L, EQ-VAS, range of motion, or radiolucent lines scoring-between the cohort operated on using PSPG and the cohort operated on using CI after 5 years of follow-up. CONCLUSION: There was no statistically significant effect of PSPGs on patient-reported outcomes or range of motion in TKA.

Computer-designed repurposing of chemical wastes into drugs.

As the chemical industry continues to produce considerable quantities of waste chemicals1,2, it is essential to devise 'circular chemistry'3-8 schemes to productively back-convert at least a portion of these unwanted materials into useful products. Despite substantial progress in the degradation of some classes of harmful chemicals9, work on 'closing the circle'-transforming waste substrates into valuable products-remains fragmented and focused on well known areas10-15. Comprehensive analyses of which valuable products are synthesizable from diverse chemical wastes are difficult because even small sets of waste substrates can, within few steps, generate millions of putative products, each synthesizable by multiple routes forming densely connected networks. Tracing all such syntheses and selecting those that also meet criteria of process and 'green' chemistries is, arguably, beyond the cognition of human chemists. Here we show how computers equipped with broad synthetic knowledge can help address this challenge. Using the forward-synthesis Allchemy platform16, we generate giant synthetic networks emanating from approximately 200 waste chemicals recycled on commercial scales, retrieve from these networks tens of thousands of routes leading to approximately 300 important drugs and agrochemicals, and algorithmically rank these syntheses according to the accepted metrics of sustainable chemistry17-19. Several of these routes we validate by experiment, including an industrially realistic demonstration on a 'pharmacy on demand' flow-chemistry platform20. Wide adoption of computerized waste-to-valuable algorithms can accelerate productive reuse of chemicals that would otherwise incur storage or disposal costs, or even pose environmental hazards.

A robotic platform for flow synthesis of organic compounds informed by AI planning.

The synthesis of complex organic molecules requires several stages, from ideation to execution, that require time and effort investment from expert chemists. Here, we report a step toward a paradigm of chemical synthesis that relieves chemists from routine tasks, combining artificial intelligence-driven synthesis planning and a robotically controlled experimental platform. Synthetic routes are proposed through generalization of millions of published chemical reactions and validated in silico to maximize their likelihood of success. Additional implementation details are determined by expert chemists and recorded in reusable recipe files, which are executed by a modular continuous-flow platform that is automatically reconfigured by a robotic arm to set up the required unit operations and carry out the reaction. This strategy for computer-augmented chemical synthesis is demonstrated for 15 drug or drug-like substances.

No radiological and clinical advantages with patient-specific positioning guides in total knee replacement.

Background and purpose - Although the use of patient-specific positioning guides (PSPGs) in total knee replacement (TKR) in theory is promising, the technique has not yet proven its superior- ity compared with the conventional method. We compared radio- logical alignment and clinical outcome between TKR performed with the use of PSPGs and the conventional operation method. Patients and methods - 3 hospitals participated in a prospec- tive trial. 109 patients were randomized to either the conventional method or to the use of PSPGs. Postoperatively a full-length standing anteroposterior radiograph and a postoperative CT scan were taken. On the CT scan the alignments were measured for both the femoral and tibial components in the frontal, sagit- tal, and axial plane. The Knee injury and Osteoarthritis Outcome Score (KOOS), the Eurocol-5D-3L (Eq5D) descriptive system and visual analogue scale (VAS), a pain score (NRS), and range of motion (ROM) were recorded preoperatively, and at 3 months, 1, and 2 years. The operation time and length of hospital stay were recorded. Results - 90 patients were available for postoperative CT mea- surements. A statistically significant difference was found between the conventional TKR instrumentation and the use of PSPGs for the frontal femoral (mean (SD) 0.6° (1.7) vs. -0.3° (2.2), CI 0.08 to 1.69) and tibial (-0.3° (1.5) vs. 0.9° (2.1), CI -1.98 to -0.44) compo- nent angles and for the tibial alignment in the sagittal plane (-3.8° (3.0) vs. -2.2° (2.5), CI -2.72; -0.42). The proportions of outliers were similar between the groups as well as the hip-knee-ankle angle, the KOOS sub scores, the Eq5D, pain (NRS), ROM, opera- tion time, and length of hospital stay. Interpretation - The use of PSPGs requires a preoperative CT scan or MRI and the guides have an additional cost. As this study was not able to prove any extra benefit of the use of PSPGs we recommend the conventional operation method for TKR.

Decomposition of Olefin Metathesis Catalysts by Brønsted Base: Metallacyclobutane Deprotonation as a Primary Deactivating Event.

Brønsted bases of widely varying strength are shown to decompose the metathesis-active Ru intermediates formed by the second-generation Hoveyda and Grubbs catalysts. Major products, in addition to propenes, are base·HCl and olefin-bound, cyclometalated dimers [RuCl(κ2-H2IMes-H)(H2C═CHR)]2 Ru-3. These are generated in ca. 90% yield on metathesis of methyl acrylate, styrene, or ethylene in the presence of either DBU, or enolates formed by nucleophilic attack of PCy3 on methyl acrylate. They also form, in lower proportions, on metathesis in the presence of the weaker base NEt3. Labeling studies reveal that the initial site of catalyst deprotonation is not the H2IMes ligand, as the cyclometalated structure of Ru-3 might suggest, but the metallacyclobutane (MCB) ring. Computational analysis supports the unexpected acidity of the MCB protons, even for the unsubstituted ring, and by implication, its overlooked role in decomposition of Ru metathesis catalysts.

Towards More Efficient, Greener Syntheses through Flow Chemistry.

Technological advances have an important role in the design of greener synthetic processes. In this Personal Account, we describe a wide range of thermal, photochemical, catalytic, and biphasic chemical transformations examined by our group. Each of these demonstrate how the merits of a continuous flow synthesis platform can align with some of the goals put forth by the Twelve Principles of Green Chemistry. In particular, we illustrate the potential for improved reaction efficiency in terms of atom economy, product yield and reaction rates, the ability to design synthetic process with chemical and solvent waste reduction in mind as well as highlight the benefits of the real-time monitoring capabilities in flow for highly controlled synthetic output.

Patient-specific positioning guides do not consistently achieve the planned implant position in UKA.

PURPOSE: To investigate whether the intended preoperative planning corresponded with the postoperative component position after medial UKA using patient-specific positioning guides (PSPGs). METHODS: Twenty-five consecutive UKAs performed with the PSPG technique (Signature™) were included. Two independent observers performed postoperative CT measurements. The preoperative angles for the femoral component were defined in the frontal plane as 0°. In the first eight cases, a femoral component with single peg was inserted, and the flexion of the femoral component was set to 5°. In the last 17 cases, a twin-peg component was used and flexion set to 10°. In the axial plane, the femoral component was on average set at 2.5° internal rotation. The preoperative tibial component angles in the frontal and axial plane were defined as 0° and in the sagittal plane as 4° in flexion. RESULTS: The postoperative femoral component angles were on average 0.8° of valgus (SD 3.2, range 12.2° valgus to 5.1° varus, n.s., CI -2.1 to 0.6), 5.0° of flexion (SD 3.9, range 10.2° flexion to 6.0° extension, p = 0.001, CI -5.3 to -1.5) and 4.0° of internal rotation (SD 1.7, range 1.4° to 6.9° int.rot., p < 0.001, CI -4.7 to -3.4). The tibial component angles were on average 3.0° of varus (SD 1.9, range 1.3° valgus to 6.8° varus, p < 0.001, CI 2.2 to 3.8), 3.2° of flexion (SD 2.4°, 6.7° flex to 1.8° ext, n.s., CI -0.2 to 1.7) and 2.7° of internal rotation (SD 7.0, range 16.6° int.rot. to 10.7° ext.rot., n.s., CI -5.6 to 0.2). CONCLUSION: This study showed no agreement between preoperative planning and postoperative component alignment (p < 0.05) for the femoral component angle in sagittal and axial plane and for the tibial component angle in the coronal plane. Although the results did not show significant difference for the tibial component angle in the axial plane, a considerable range of the component angles was found varying from 17° internal to 11° external rotation. This study suggests that the use of PSPGs for UKA does not lead to consistent component position. LEVEL OF EVIDENCE: IV.

A General Decomposition Pathway for Phosphine-Stabilized Metathesis Catalysts: Lewis Donors Accelerate Methylidene Abstraction.

Sterically accessible Lewis donors are shown to accelerate decomposition during catalysis, for a broad range of Grubbs-class metathesis catalysts. These include benzylidene derivatives RuCl2(NHC)(PCy3)(═CHPh) (Ru-2: NHC = H2IMes, a; IMes, b; H2IPr, c; IPr, d; H2ITol, e) and indenylidene complexes RuCl2(NHC)(PCy3)(═C15H10) (NHC = H2IMes, Ru-2f; IMes, Ru-2g). All of these precatalysts form methylidene complex RuCl2(NHC)(═CH2) Ru-3 as the active species in metathesis of terminal olefins, and generate RuCl2(NHC)(PCy3)(═CH2) Ru-4 as the catalyst resting state. On treatment with a 10-fold excess of pyridine, Ru-4a and Ru-4b decomposed within minutes in solution at RT, eliminating [MePCy3]Cl A by net loss of three ligands (PCy3, methylidene, and one chloride), and a mesityl proton. In comparison, loss of A from Ru-4a in the absence of a donor requires up to 3 days at 55 °C. The σ-alkyl intermediate RuCl2(13CH2PCy3)(NHC) (py)2 resulting from nucleophilic attack of free PCy3 on the methylidene ligand was undetectable for the H2IMes system, but was spectroscopically observable for the IMes system. The relevance of this pathway to decomposition of catalysts Ru-2a-g was demonstrated by assessing the impact of pyridine on the in situ-generated methylidene species. Slow initiation (as observed for the indenylidene catalysts) did not protect against methylidene abstraction. Importantly, studies with Ru-4a and Ru-4b indicated that weaker donors (THF, MeCN, DMSO, MeOH, and even H2O) likewise promote this pathway, at rates that increase with donor concentration, and severely degrade catalyst productivity in RCM, even for a readily cyclized substrate. In all cases, A was the sole or major 31P-containing decomposition product. For DMSO, a first-order dependence of decomposition rates on DMSO concentration was established. This behavior sends a warning about the use of phosphine-stabilized metathesis catalysts in donor solvents, or with substrates bearing readily accessible donor sites. Addition of pyridine to RuCl2(H2IMes)(PCy3)(═CHMe) did not result in ethylidene abstraction, indicating that this decomposition pathway can be inhibited by use of substrates in which the olefin bears a ß-methyl group.

Olefin Metathesis at the Dawn of Implementation in Pharmaceutical and Specialty-Chemicals Manufacturing.

The recent uptake of molecular metathesis catalysts in specialty-chemicals and pharmaceutical manufacturing is reviewed.

The divergent effects of strong NHC donation in catalysis.

Strong σ-donation from NHC ligands (NHC = N-heterocyclic carbene) is shown to have profoundly conflicting consequences for the reactivity of transition-metal catalysts. Such donation is regarded as central to high catalyst activity in many contexts, of which the second-generation Grubbs metathesis catalysts (RuCl2(NHC)(PCy3)([double bond, length as m-dash]CHPh), GII) offer an early, prominent example. Less widely recognized is the dramatically inhibiting impact of NHC ligation on initiation of GII, and on re-entry into the catalytic cycle from the resting-state methylidene species RuCl2(NHC)(PCy3)([double bond, length as m-dash]CH2), GIIm. Both GII and the methylidene complexes are activated by dissociation of PCy3. The impact of NHC donicity on the rate of PCy3 loss is explored in a comparison of s-GIIm, vs. u-GIIm, in which the NHC ligand is saturated H2IMes or unsaturated IMes, respectively. PCy3 loss is nearly an order of magnitude slower for the IMes derivative (a difference that is replicated, albeit smaller, for the benzylidene precatalysts GII). Proposed as an overlooked contributor to these rate differences is an increase in the Ru-PCy3 bond strength arising from π-back-donation onto the phosphine ligand. Strong σ-donation from the IMes ligand, coupled with the inability of this unsaturated NHC to participate in significant π-backbonding, amplifies Ru → PCy3 π-back-donation. The resulting increase in Ru-P bond strength greatly inhibits entry into the active cycle. For s-GII, in contrast, the greater π-acceptor capacity of the NHC ligand enables competing Ru → H2IMes back-donation (as confirmed by NOE experiments, which reveal restricted rotation about the Ru-NHC bond for H2IMes, but not IMes). Ru → PCy3 back-donation is thus attenuated in the H2IMes complexes, accounting for the greater lability of the PCy3 ligand in s-GIIm and s-GII. Similarly inhibited initiation is predicted for other metal-NHC catalysts in which a π-acceptor ligand L must be dissociated to permit substrate binding. Conversely, enhanced reactivity can be expected where such L ligands are pure σ-donors. These effects are expected to be particularly dramatic where the NHC ligand has minimal π-acceptor capacity (as in the unsaturated Arduengo carbenes), and in geometries that maximize NHC-M-L orbital interactions.

Comparison of planned and achieved implant position in total knee arthroplasty with patient-specific positioning guides.

BACKGROUND AND PURPOSE: Intraoperatively, patient-specific positioning guides (PSPGs) represent the preoperatively planned alignment. We investigated the degree of correlation between preoperative planning and the alignment achieved postoperatively with the PSPG technique. PATIENTS AND METHODS: TKAs performed with the PSPG technique between 2009 and 2011 were included. 39 patients (42 TKAs) volunteered for a postoperative CT scan. 2 independent observers performed the postoperative CT measurements. Preoperative component angles (target angles) in the coronal and axial planes were defined as 0 degrees, and in the sagittal plane on average 2.8 degrees for the femoral component and 3 degrees for the tibial component. A postoperative full-length standing anteroposterior radiograph was carried out in 41 TKAs. RESULTS: The femoral component was on average 1.2 (SD 1.5) degrees in varus, 4.4 (SD 4.0) degrees in flexion, and 0.5 (SD 1.4) degrees in external rotation. The tibial component was on average 0.4 (SD 2.5) degrees in varus and 3.7 (SD 2.3) degrees in flexion. A statistically significant difference between the target (preoperative software plan) and postoperative CT measurement was found for the femoral component angle in the frontal plane (p < 0.001; CI: 0.8-1.7), the sagittal plane (p = 0.01; CI -5.6 to -3.1), and the axial plane (p = 0.03; CI: 0.04-0.88). HKA angles were greater than 3 degrees from the neutral axis in 10 of the 41 cases. INTERPRETATION: We found our postoperative component alignment angles to be close to the software plan, especially for the tibial component. However, we found outliers in all planes and we cannot therefore conclude that the PSPG technique is a method that reproduces preoperatively planned alignment in a consistent manner.

Chemical plants: high-value molecules from essential oils.

As society faces a future of dwindling petrochemical supplies at increasing cost, much attention has been focused on methods to degrade biomass into renewable commodity-chemical building blocks. Reported here is a powerful complementary approach that amplifies the complexity of molecular structures present in plant materials. Essential-oil phenylpropenoids are transformed via acrylate cross-metathesis into potent antioxidants that are widely used in perfumery and cosmetics, and in treating disorders associated with oxidative damage.

Ethylene-promoted versus ethylene-free enyne metathesis.

The role of ethylene in promoting metathesis of acetylenic enynes is probed within the context of ring-closing enyne metathesis, using first- and second-generation Grubbs catalysts. Under inert atmosphere, rapid catalyst deactivation is observed by calibrated GC-FID analysis for substrates with minimal propargylic bulk. MALDI-TOF mass spectra reveal a Ru(enyne)(2) derivative that exhibits very low reactivity toward both enyne and ethylene. Under ethylene, formation of this species is suppressed. Enynes with bulky propargylic groups are not susceptible to this catalyst deactivation pathway, even under N(2) atmosphere.

Monitoring of laryngopharyngeal reflux: influence of meals and beverages.

Ambulatory 24-hour double-probe pH monitoring seems to be the best test to measure reflux. Artifacts caused by intake of acid foods and beverages have to be excluded, necessitating a time-consuming manual review of the 24-hour data. Dietary restrictions used to bypass these artifacts would interfere with the normal daily life situation. Therefore, the influence of food and beverages ingested during the monitoring period was studied. Data from 252 patients who underwent double-probe pH monitoring were analyzed, first by visual inspection of the 24-hour tracing and second by leaving out the intake periods. As to the registration of gastroesophageal reflux, the inclusion or omission of meals and beverages hardly influenced the data. However, the registration of laryngopharyngeal reflux was severely biased by intake of food and beverages and other artifacts. Leaving out meals and beverages did not correct for all artifacts. Therefore, we recommend review of each laryngopharyngeal pH drop.

Identification of AtPIS, a phosphatidylinositol synthase from Arabidopsis.

Phosphatidylinositol synthase is the enzyme responsible for the synthesis of phosphatidylinositol, a key phospholipid component of all eukaryotic membranes and the precursor of messenger molecules involved in signal transduction pathways for calcium-dependent responses in the cell. Using the amino acid sequence of the yeast enzyme as a probe, we identified an Arabidopsis expressed sequence tag potentially encoding the plant enzyme. Sequencing the entire cDNA confirmed the homology between the two proteins. Functional assays, performed by overexpression of the plant cDNA in Escherichia coli, a bacteria which lacks phosphatidylinositol and phosphatidylinositol synthase activity, showed that the plant protein induced the accumulation of phosphatidylinositol in the bacterial cells. Analysis of the enzymatic activity in vitro showed that synthesis of phosphatidylinositol occurs when CDP-diacylglycerol and myo-inositol only are provided as substrates, that it requires manganese or magnesium ions for activity, and that it is at least in part located to the bacterial membrane fraction. These data allowed us to conclude that the Arabidopsis cDNA codes for a phosphatidylinositol synthase. A single AtPIS genetic locus was found, which we mapped to Arabidopsis chromosome 1.

Compared selectivities of the phosphatidylinositol-synthase from maize coleoptiles either in microsomal membranes or after solubilization.

PI-synthase selectivity from etiolated maize coleptiles was studied either associated with the microsomal membranes or after solubilization by CHAPS and prepurification on a DEAE-trisacryl M column. When maize microsomes were incubated with [3H]inositol without any exogenous CPM-PA, the most heavily labelled molecular species were 16:0/18:2-PI (77%), 16:0/18:3-plus 18:2/18:2-PI (15%), 16:0/18:1-PI (4%) and 18:0/18:2-PI (4%). Addition to the incubation medium of up to 300 microM 16:0/16:0-CMP-PA unexpectedly resulted in the formation of very little labelled 16:0/16:0-PI. When the solubilized fraction from microsomes was incubated with [3H]inositol in absence of 16:0/16:0-CPM-PA, the same PI molecular species as above were synthesized. However, with increasing concentrations of 16:0/16:0-CMP-PA in the medium, increasing amounts of labelled 16:0/16:0-PI appeared as well. With prepurified PI-synthase eluted from a DEAE column, endogenous CMP-PA was poorly utilized for PI biosynthesis whereas the exogenous 16:0/16:0-CPM-PA was used actively. With time, the endogenous CMP-PA was utilized first and the exogenous substrate was utilized, albeit, much more slowly. The results demonstrate that the selectivity displayed by PI-synthase towards various molecular species of CMP-PA depends on the integration of the enzyme in the membrane structure. Solubilization of the enzyme, i.e., inclusion of the protein in micelles with detergents and lipids, results in an apparent loss of the selectivity for CMP-PA.

Biosynthesis of eukaryotic lipid molecular species by the cyanobacterium Spirulina platensis.

This report brings evidence that a prokaryotic photosynthetic organism can synthesize eukaryotic molecular species of glycerolipids. When Spirulina platensis PCC 8005 was supplemented with oleic acid, the sum of the percentages of 18 carbon (C18) fatty acids in monogalactosyldiacylglycerol (MGDG), the major lipid class, became largely higher than 50 mol%. This was absolutely unexpected from the well-known structure of cyanobacterial lipids. In these organisms, C18 fatty acids usually account for less than 50 mol% because they are esterified on carbon 1 of the glycerol, exclusively. This classical feature was 99% confirmed in control as well as in palmitate-supplemented cultures. The major molecular species of MGDG, which resulted from the different distributions of fatty acids on carbons 1 and 2 of glycerol, were C18/C16 type, belonging to the so-called "prokaryotic" type of lipids. By contrast, the molecular species of MGDG from oleate-supplemented cultures consisted of only 74 mol% of C18/C16 and the complementary 26 mol% were C18/C18, the so-called "eukaryotic" type of lipids. Furthermore, such C18/C18 lipids were also evidenced as traces (< 1%) in control cultures. These results underline the fact that the fatty acid specificity of 1-monoacylglycerol-3-phosphate-acyltransferase (in Spirulina) is not as absolute as the widely accepted concept of prokaryotic lipid would suggest. Oleate, supplemented at high concentration, can be compelled to act as a substrate for the acyltransferase and this results in the appearance of C18/C18 "eukaryotic" lipids in a prokaryotic organism.

Comparison of the molecular species patterns of phosphatidic acid, CDP-diacylglycerols and phosphatidylinositol in potato tuber, pea leaf and soya-bean microsomes: consequences for the selectivity of the enzymes catalyzing phosphatidylinositol biosynthesis.

Microsomes prepared from pea leaf, potato tuber or germinated soya-beans, were incubated for 30 min with [14C]glycerol 3-phosphate. In the three tissues, phosphatidic acid (PA), CDP-diacylglycerols (CMP-PA) and phosphatidylinositol (PI) were labelled and could be separated by TLC. After methylation of phosphatidic acid, or treatment of CMP-PA by a nucleotidase, the molecular species composition of the three lipid classes could be determined by radio-HPLC. The similarity observed between the distributions of radioactivity among CMP-PA and PA molecular species, in the three tissues, indicates that the enzyme CTP:PA cytidylyltransferase did not present any selectivity towards any molecular species of PA. In contrast, only two molecular species containing palmitic acid (16:0/18:2 and 16:0/18:3) were labelled in PI whereas labelled PA and CMP-PA contained molecular species possessing stearic acid (18:0/18:2, 18:0/18:3 and 18:0/18:1). This indicates that the enzyme PI-synthase utilizes preferentially those molecular species of CMP-PA containing palmitic acid as substrates. However, mass analyses of PI prepared from the microsomes of the three tissues used in this study, indicated the presence of molecular species containing stearic acid (18:0/18:2 and 18:2/18:2). Except in soya-bean microsomes (where 18:0/18:2-PI represented 16% of total PI), those last molecular species were always present in small amounts.

Regulation by Lipids of Plant Microsomal Enzymes: III. Phospholipid Dependence of the Cytidine-Diphospho-Choline Phosphotransferase of Potato Microsomes.

Cytidine-diphospho-choline diacyl-glycerol phosphorylcholine phosphotransferase activity was demonstrated in potato (Solanum tuberosum L.) microsomes and the incorporation of cytidine-diphospho[(14)C]choline into phosphatidylcholine was characterized by the time course of (14)C incorporation and the effect of microsomal protein concentration on choline incorporation.Potato microsomes were progressively delipidated by treatments (2 min at 0 degrees C) with increasing amounts of phospholipase C from Bacillus cereus. A decrease in choline phosphotransferase activity was observed in parallel with the progressive hydrolysis of membrane phospholipids. A 70% (or more) phospholipid hydrolysis provoked the total inactivation of the enzyme.Adding back exogenous phospholipids (in the form of liposomes) to phospholipase C-treated membranes restored the enzymic activity. Restoration could be obtained with egg yolk phospholipids as well as with potato phospholipids. Restoration was time dependent and completed after 10 minutes; restoration was also dependent on the quantity of liposomes added to lipid-depleted membranes: the best restorations were obtained with 1 to 2.5 milligrams of phospholipid per mg of microsomal protein; higher phospholipid to protein ratios were less efficient or inhibitory.These results clearly demonstrate the phospholipid dependence of the cytidine-diphospho-choline phosphotransferase from potato microsomes.