131 The Health-Related Quality of Life of Patients Waiting for Anterior Cruciate Ligament Reconstruction Is Worse Than an Age and Sex Match Population: Increasing Time on Waiting List Was Independently Associated With a Worse Quality of Life

Aim

To assess the health-related quality of life (HRQoL) of patients waiting for an anterior cruciate ligament (ACL) reconstruction compared to the population at risk, and whether knee specific function was predictive of HRQoL and to identify factors associated with a worse HRQoL.

Method

Sixty-seven patients (male n = 50, female n = 17, mean age 29) identified from the surgical waiting list completed a questionnaire that included demographics, BMI, time of injury, EuroQol 5-demension (EQ-5D), short-form (SF-)36 and International Knee Documentation Committee (IKDC) scores. Age and sex matched HRQoL data were obtained from population level data.

Results

The mean EQ-5D score for the study cohort was significantly worse than the matched score (difference 0.367, p<0.001), and the same trend was observed for all eight dimensions of the SF-36 score. Thirty-three (49%) patients felt their health in general was somewhat or much worse compared to one-year ago. There was a correlation between the IKDC and EQ-5D scores (r = 0.540, p<0.001), and linear regression was used to formulate the EQ-5D score: EQ-5D = (IKDCx0.013)–0.015(constant). The SF-36 physical component and the length of time on the waiting list were independently associated the HRQoL, with each 14-point drop or for every 200-days a clinically significant deterioration in a patients HRQoL occurred, respectively.

Conclusions

Patients had a significantly worse HRQoL when compared to age and sex match population, which deteriorates with worsening physical function and increasing length of time on the waiting list. The knee specific IKDC correlated with HRQoL and could be used to estimate the EQ-5D score.

Autonomous robotic laparoscopic surgery for intestinal anastomosis

Autonomous robotic surgery has the potential to provide efficacy, safety, and consistency independent of individual surgeon's skill and experience. Autonomous anastomosis is a challenging soft-tissue surgery task because it requires intricate imaging, tissue tracking, and surgical planning techniques, as well as a precise execution via highly adaptable control strategies often in unstructured and deformable environments. In the laparoscopic setting, such surgeries are even more challenging because of the need for high maneuverability and repeatability under motion and vision constraints. Here we describe an enhanced autonomous strategy for laparoscopic soft tissue surgery and demonstrate robotic laparoscopic small bowel anastomosis in phantom and in vivo intestinal tissues. This enhanced autonomous strategy allows the operator to select among autonomously generated surgical plans and the robot executes a wide range of tasks independently. We then use our enhanced autonomous strategy to perform in vivo autonomous robotic laparoscopic surgery for intestinal anastomosis on porcine models over a 1-week survival period. We compared the anastomosis quality criteria-including needle placement corrections, suture spacing, suture bite size, completion time, lumen patency, and leak pressure-of the developed autonomous system, manual laparoscopic surgery, and robot-assisted surgery (RAS). Data from a phantom model indicate that our system outperforms expert surgeons' manual technique and RAS technique in terms of consistency and accuracy. This was also replicated in the in vivo model. These results demonstrate that surgical robots exhibiting high levels of autonomy have the potential to improve consistency, patient outcomes, and access to a standard surgical technique.

Supervised Autonomous Electrosurgery via Biocompatible Near-Infrared Tissue Tracking Techniques

Autonomous robotic surgery systems aim to improve patient outcomes by leveraging the repeatability and consistency of automation and also reducing human induced errors. However, intraoperative autonomous soft tissue tracking and robot control still remains a challenge due to the lack of structure, and high deformability of such tissues. In this paper, we take advantage of biocompatible Near-Infrared (NIR) marking methods and develop a supervised autonomous 3D path planning, filtering, and control strategy for our Smart Tissue Autonomous Robot (STAR) to enable precise and consistent incisions on complex 3D soft tissues. Our experimental results on cadaver porcine tongue samples indicate that the proposed strategy reduces surface incision error and depth incision error by 40.03% and 51.5%, respectively, compared to a teleoperation strategy via da Vinci. Furthermore, compared to an autonomous path planning method with linear interpolation between the NIR markers, the proposed strategy reduces the incision depth error by 48.58% by taking advantage of 3D tissue surface information.

Semi-autonomous Robotic Anastomoses of Vaginal Cuffs Using Marker Enhanced 3D Imaging and Path Planning

Autonomous robotic anastomosis has the potential to improve surgical outcomes by performing more consistent suture spacing and bite size compared to manual anastomosis. However, due to soft tissue's irregular shape and unpredictable deformation, performing autonomous robotic anastomosis without continuous tissue detection and three-dimensional path planning strategies remains a challenging task. In this paper, we present a novel three-dimensional path planning algorithm for Smart Tissue Autonomous Robot (STAR) to enable semi-autonomous robotic anastomosis on deformable tissue. The algorithm incorporates (i) continuous detection of 3D near infrared (NIR) markers manually placed on deformable tissue before the procedure, (ii) generating a uniform and consistent suture placement plan using 3D path planning methods based on the locations of the NIR markers, and (iii) updating the remaining suture plan after each completed stitch using a non-rigid registration technique to account for tissue deformation during anastomosis. We evaluate the path planning algorithm for accuracy and consistency by comparing the anastomosis of synthetic vaginal cuff tissue completed by STAR and a surgeon. Our test results indicate that STAR using the proposed method achieves 2.6 times better consistency in suture spacing and 2.4 times better consistency in suture bite sizes than the manual anastomosis.

The prognostic value of the fracture level in the treatment of Gartland type III supracondylar humeral fracture in children

A small proportion of children with Gartland type III supracondylar humeral fracture (SCHF) experience troubling limited or delayed recovery after operative treatment. We hypothesised that the fracture level relative to the isthmus of the humerus would affect the outcome. We retrospectively reviewed 230 children who underwent closed reduction and percutaneous pinning (CRPP) for their Gartland type III SCHFs between March 2003 and December 2012. There were 144 boys and 86 girls, with the mean age of six years (1.1 to 15.2). The clinico-radiological characteristics and surgical outcomes (recovery of the elbow range of movement, post-operative angulation, and the final Flynn grade) were recorded. Multivariate analysis was employed to identify prognostic factors that influenced outcome, including fracture level. Multivariate analysis revealed that a fracture below the humeral isthmus was significantly associated with poor prognosis in terms of the range of elbow movement (p < 0.001), angulation (p = 0.001) and Flynn grade (p = 0.003). Age over ten years was also a poor prognostic factor for recovery of the range of elbow movement (p = 0.027). This is the first study demonstrating a subclassification system of Gartland III fractures with prognostic significance. This will guide surgeons in peri-operative planning and counselling as well as directing future research aimed at improving outcomes.

Dosimetric advantages and superior treatment delivery efficiency of RapidArc over conventional intensity-modulated radiotherapy in high-risk prostate cancer involving seminal vesicles and pelvic nodes

AIMS

To compare the dosimetry and treatment delivery efficiency of RapidArc with conventional intensity-modulated radiotherapy (IMRT) in the treatment of high-risk prostate cancer.

MATERIALS AND METHODS

Fifteen patients with high-risk localised prostate cancer were studied. Sequential treatment was used. The initial planning target volume (PTV-L) included the prostate, seminal vesicles and pelvic lymphatics, whereas the prostate boost PTV (PTV-P) included the prostate and seminal vesicles only. The total prescription dose was 76 Gy (44 Gy to PTV-L, 32 Gy to PTV-P; 2 Gy/fraction). Two separate planning techniques were generated for each patient: seven static-field IMRT versus two-arc RapidArc. Dose-volume parameters for the organs at risk, conformity index and homogeneity index for the PTVs, the calculated monitor units and treatment delivery time for both techniques were compared.

RESULTS

RapidArc gave more conformal plans than IMRT for both PTVs. RapidArc gave a higher homogeneity index to the PTV-P and a similar homogeneity index to the PTV-L. The two techniques gave similar dosimetric results for the rectum, bladder and femoral heads. The mean dose (Dmean) and the maximum dose (Dmax) of the bowel space were reduced by 3.06 and 2.83%, respectively, with RapidArc. The V20 Gy, V30 Gy and V40 Gy for healthy tissues were reduced by 7.77, 14.25 and 17.55%, respectively, with RapidArc. The calculated treatment delivery time and monitor units were reduced by 74.09%/60.93% and 68.32%/48.06% for the PTV-L/PTV-P, respectively, with RapidArc.

CONCLUSION

RapidArc is better than conventional IMRT in terms of dosimetry and delivery efficiency for high-risk prostate cancer.

Risk factors for overgrowth after flexible intramedullary nailing for fractures of the femoral shaft in children

We analysed retrospectively the risk factors leading to femoral overgrowth after flexible intramedullary nailing in 43 children (mean age 7.1 years (3.6 to 12.0)) with fractures of the shaft of the femur. We reviewed their demographic data, mechanism of injury, associated injuries, the type and location of the fractures, the nail–canal diameter (NCD) ratios and femoral overgrowth at a mean follow-up of 40.7 months (25.2 to 92.7). At that time, the children were divided into two groups, those with femoral overgrowth of < 1 cm (Group 1), and those with overgrowth of ≥ 1 cm (Group 2). The mean femoral overgrowth of all patients was 0.6 cm at final follow-up. Overgrowth of ≥ 1 cm was noted in 11 children (25.6%). The NCD ratio was significantly lower in Group 2 than in Group 1, with an odds ratio of 30.0 (p = 0.003).

We believe that a low NCD ratio is an indicator of an unstable configuration with flexible intramedullary nailing, and have identified an association between a low NCD ratio and femoral overgrowth resulting in leg-length discrepancy after flexible intramedullary nailing in paediatric femoral shaft fractures.

Cite this article: Bone Joint J 2013;95-B:254–8.

Chimeric vaccine composed of viral peptide and mammalian heat-shock protein 60 peptide protects against West Nile virus challenge

The protective efficacy and immunogenicity of a chimeric peptide against West Nile virus (WNV) was evaluated. This virus is the aetiological agent of West Nile fever, which has recently emerged in the western hemisphere. The rapid spread of WNV throughout North America, as well as the constantly changing epidemiology and transmission of the virus by blood transfusion and transplantation, have raised major public-health concerns. Currently, there are no effective treatments for WNV or vaccine for human use. We previously identified a novel, continuous B-cell epitope from domain III of the WNV envelope protein, termed Ep15. To test whether this epitope can protect against WNV infection, we synthesized a linear chimeric peptide composed of Ep15 and the heat-shock protein 60 peptide, p458. The p458 peptide is an effective carrier peptide for subunit vaccines against other infectious agents. We now report that mice immunized with the chimeric peptide, p458-Ep15, were resistant to lethal challenges with three different WNV strains. Moreover, their brains were free of viral genome and infectious virus. Mice immunized with Ep15 alone or with p431-Ep15, a control conjugate, were not protected. The chimeric p458-Ep15 peptide induced WNV-specific immunoglobulin G antibodies that neutralized the virus and induced the secretion of interferon-gammain vitro. Challenge of chimeric peptide-immunized mice considerably enhanced WNV-specific neutralizing antibodies. We conclude that this chimeric peptide can be used for formulation of a human vaccine against WNV.

Phase II study of gefitinib in metastatic or locoregionally recurrent nasopharyngeal carcinoma (NPC)

15509

Background: Our preclinical work has shown that epidermal growth factor receptor (EGFR) is expressed in ∼ 80% of undifferentiated NPC & gefitinib is a small molecule inhibitor against EGFR with anti-proliferative activity in NPC in vitro. Methods: We report the preliminary result of a phase II study of gefitinib in patients (pts) who progressed after 1–2 lines of chemotherapy (at least 1 line had to contain platinum) for metastatic or locoregionally recurrent NPC. Fourteen Chinese pts were accrued, of whom the median age was 48 years (range 34–64 years), 12 were males, 9 had metastatic & 5 had locoregionally recurrent NPC. All received gefitinib at 500mg/day orally, every 28 days with radiological assessment performed every 2 cycles for a maximum of 8 cycles. Ten pts had 1 line & 5 pts had 2 lines of prior chemotherapy. Results: The median number of administered cycles was 2 (range 1–8). Of the 14 pts evaluable for toxicity, the most commonly reported were acneiform rash (86%, grade 1–2, n = 10; grade 3, n = 4), dry skin (86%, grade 1–2), diarrhea (71%, grade 1–2), fatigue (64%, grade 1–2), anorexia (64%, grade 1–2) & nausea (20%, grade 2). Other grade 3–4 toxicities included fever (n = 2, skin cellulitis, infective pneumonia), hyponatremia (n = 2), near-syncope (n = 2), anemia (n = 1). Dose reduction to 250mg/day was required in 4 pts who encountered grade 3 skin rash. Of the 11 pts evaluable for response, 2 had stable disease (SD) for ≥ 6 months (m) (mean 6.8 m) 9 progressed and no partial responders. Five pts have died mostly of progressive disease & there were no treatment-related deaths. Conclusions: Gefitinib is well tolerated in pts with advanced NPC with some pts experiencing disease stabilization for over 6 months & study accrual is ongoing.

No significant financial relationships to disclose.

Signature authentication by forensic document examiners

We report on the first controlled study comparing the abilities of forensic document examiners (FDEs) and laypersons in the area of signature examination. Laypersons and professional FDEs were given the same signature-authentication/simulation-detection task. They compared six known signatures generated by the same person with six unknown signatures. No a priori knowledge of the distribution of genuine and nongenuine signatures in the unknown signature set was available to test-takers. Three different monetary incentive schemes were implemented to motivate the laypersons. We provide two major findings: (i) the data provided by FDEs and by laypersons in our tests were significantly different (namely, the hypothesis that there is no difference between the assessments provided by FDEs and laypersons about genuineness and nongenuineness of signatures was rejected); and (ii) the error rates exhibited by the FDEs were much smaller than those of the laypersons. In addition, we found no statistically significant differences between the data sets obtained from laypersons who received different monetary incentives. The most pronounced differences in error rates appeared when nongenuine signatures were declared authentic (Type I error) and when authentic signatures were declared nongenuine (Type II error). Type I error was made by FDEs in 0.49% of the cases, but laypersons made it in 6.47% of the cases. Type II error was made by FDEs in 7.05% of the cases, but laypersons made it in 26.1% of the cases.

Fiber digestion and energy utilization of fat sand rats (Psammomys obesus) consuming the chenopod Anabasis articulata

Most herbivorous rodents consume a variety of plants and, when available, select ones low in fiber content. In contrast, the fat sand rat (Psammomys obesus), a diurnal gerbillid rodent that is wholly herbivorous, is able to survive while consuming only the halophytic chenopod Anabasis articulata. We hypothesized that these gerbils are able to digest chenopods efficiently and that fiber digestion contributes substantially to their energy budget. Digestibility of total fibers (NDF), hemicellulose, and cellulose was 51.6%, 66.4%, and 44.0%, respectively. Energy derived from fiber digestion was 211.7 kJ kg(-0.75) d(-1) and resulted mostly from hemicellulose digestion. Average daily metabolic rate was 658.4 kJ kg(-0.75) d(-1), and basal metabolic rate (BMR) was determined to be close to 192.6 kJ kg(-0.75) d(-1). Therefore, fiber digestion provided 32% of maintenance requirements and 110% of BMR requirements, one of the highest values reported thus far for placental mammals. The efficiency of utilization of the chenopod was 0.29, a low value compared to other dietary items. We concluded that A. articulata fulfills all the energy and nutrient requirements of fat sand rats, even though energy yields and efficiency of utilization of its energy is low.

Level of energy intake affects the estrous cycle in Sundevall's jird (Meriones crassus)

Effects of energy intake on the estrous cycle of the desert gerbillid, Sundevall's jird (Meriones crassus; 80 g; n=22) were studied. Females were offered either maintenance or below maintenance levels of millet seeds and ad lib. Atriplex halimus leaves and stems; drinking water was not available. Vaginal smears were used to determine sexual stage. We hypothesized that the estrous cycle ceases at low levels of energy intake and commences when sufficient energy is available. Females lost body mass linearly with a decrease in metabolizable energy intake. Estrous cycle averaged 4.46 d at maintenance energy intake but increased to an average of 7.81 d at 70% of maintenance energy intake. A cessation of the cycle occurred at an energy intake below 70% of maintenance requirements, which resulted in a body mass loss of more than 1% per day. More variability in the length of the different stages of the cycle was found with lower levels of energy intake. When offered ad lib. millet seeds and A. halimus (n=14), recovery to the normal cycle was attained within 10 d by 43% of the females and within 16 d by the rest of the females. Recovery time was longest in females that previously had the lowest energy intake. We concluded that the estrous cycle of M. crassus is sensitive to energy intake. With restricted energy intake, the estrous cycle and reproductive activities cease but can be restored with provision of adequate energy. This strategy ensures that reproduction occurs when conditions of food availability and body condition of the females are favorable.

Modulation of circulatory residence of recombinant acetylcholinesterase through biochemical or genetic manipulation of sialylation levels

Sialylation of N-glycans associated with recombinant human acetylcholinesterase (rHuAChE) has a central role in determining its circulatory clearance rate. Human embryonal kidney 293 (HEK-293) cells, which are widely used for the expression of recombinant proteins, seem to be limited in their ability to sialylate overexpressed rHuAChE. High-resolution N-glycan structural analysis, by gel permeation, HPLC anion-exchange chromatography and high-pH anion-exchange chromatography (HPAEC), revealed that the N-glycans associated with rHuAChE produced in HEK-293 cells belong mainly to the complex-biantennary class and are only partly sialylated, with approx. 60% of the glycans being monosialylated. This partial sialylation characterizes rHuAChE produced by cells selected for high-level expression of the recombinant protein. In low-level producer lines, the enzyme exhibits a higher sialic acid content, suggesting that undersialylation of rHuAChE in high-level producer lines stems from a limited endogenous glycosyltransferase activity. To improve sialylation in HEK-293 cells, rat liver beta-galactoside alpha-2,6-sialyltransferase cDNA was stably transfected into cells expressing high levels of rHuAChE. rHuAChE produced by the modified cells displayed a significantly higher proportion of fully sialylated glycans as shown by sialic acid incorporation assays, direct measurement of sialic acid, and HPAEC glycan profiling. Genetically modified sialylated rHuAChE exhibited increased circulatory retention (the slow-phase half-life, t12beta, was 130 min, compared with 80 min for the undersialylated enzyme). Interestingly, the same increase in circulatory residence was observed when rHuAChE was subjected to extensive sialylation in vitro. The engineered HEK-293 cells in which the glycosylation machinery was modified might represent a valuable tool for the high level of expression of recombinant glycoproteins whose sialic acid content is important for their function or for pharmacokinetic behaviour.

Energy budget in free-living animals: a novel approach based on the doubly labeled water method

We provide a theoretical and practical model for the calculation of energy balance of free-living animals using the doubly labeled water method. Energy expenditure, metabolizable energy intake, and body energy balance (energy retention, negative or positive) of animals are estimated using CO2 production, water influx, and dietary habits. This model accounts for CO2 produced from the 1) oxidation of dietary substrates, 2) catabolism of body tissue, and 3) deposition of body energy. We examined the model using data from studies on five homeotherms reported in the literature. The ratios between daily energy expenditure using our model and that presented in the reports ranged between 0.76 and 1.18. Metabolizable energy intakes were as low as 43% of energy expenditure in negative energy-balanced hummingbirds and as high as 245% of energy expenditure in positive energy-balanced koala bears. This model is the first that allows theoretical calculation of all energy budget components, including energy retention, in free-living animals using the doubly labeled water method.

A counterexample to the Alexopoulos-Griffin path planning algorithm

The planar stationary-obstacle path-planning problem for polygonal obstacles has been correctly and completely solved by T. Lozano-Perez and M. Wesley (1979), i.e., a global, optimal algorithm was provided which requires O(mu(2)logmu) computation time, where mu is the number of obstacle-faces in the scene. That algorithm is known as the VGRAPH algorithm. Two variants of VGRAPH have been developed to solve the same problem in O(mu(2)) computation time. Our paper discusses a recent algorithm proposed by C. Alexopoulos and P.M. Griffin (1992), called V*GRAPH, which also claims to provide an optimal solution. We demonstrate by counter-example that V*GRAPH is neither global nor optimal.

On the moving-obstacle path-planning algorithm of Shih, Lee, and Gruver

We analyze a motion planning algorithm proposed by Shih, Lee, and Gruver (1990). In particular, we discuss the case of motion planning among moving obstacles, for which an algorithm is presented by Shih, Lee, and Gruver (1990). The algorithm is claimed to always yield a collision-free path when one exists. We provide a specific counter-example to this claim, examine the possibility of repairing the algorithm, and discuss the computational complexity of a corrected algorithm.

Specificity in the recognition of crystals by antibodies

We show that IgG molecules isolated from the serum of rabbits injected with crystals of monosodium urate monohydrate, magnesium urate octahydrate and allopurinol, can each catalyze the nucleation of the same type of crystal to which they were exposed. These results generalize previous findings related to monosodium urate monohydrate and assess the idea that the invasion of a foreign crystal into an organism may amplify a population of antibodies which bear in their binding sites an imprint of the crystal surface structure. Such antibodies can further act as nucleating templates which accelerate crystal formation in vitro. Antibodies isolated from rabbits injected with sodium urate crystals do not cross-react or cross-react only to a low extent with antibodies isolated from rabbits injected with crystals of either magnesium urate or allopurinol. These results indicate a high specificity of the elicited antibodies, as these can distinguish between nuclei of crystals having similar molecular and structural characteristics.

Seasonal plasma levels of luteinizing and steroid hormones in male and female domestic ostriches (Struthio camelus)

Ostriches are low-latitude birds and can be considered to be seasonal breeders. However, they are also opportunistic in that they can breed all year round. Monthly hormonal plasma concentrations were measured in six female and six male domestic ostriches kept at a latitude of 31 degrees 20'N. Measurements were made over a year, during which time each female laid an average of 28.7 eggs. Egg laying occurred between March and September, with peak numbers in May-June. Concentrations of plasma luteinizing hormone (LH) increased in February in both sexes and started declining before termination of egg laying. Plasma testosterone concentrations in males increased in April, about 2 months after the increase in LH. In females, plasma estradiol concentrations peaked in May but were elevated from March to August, basically all of the egg-laying period. Plasma hormonal changes in the ostriches were gradual and not abrupt, as seen in many wild seasonal breeders of higher latitude.

Antibodies against crystals

We suggest that crystals, when introduced into an organism, may behave as conventional antigens, mediating the production of specific antibodies. These antibodies would bear an imprint of the crystal surface and may consequently behave as a nucleating matrix in a new crystallization event. Thus, they would behave as catalytic antibodies. We show that IgG antibodies isolated from patients suffering from gout, a joint disease caused by crystals of monosodium urate monohydrate (MSUM), accelerate the appearance of new crystals of MSUM from a supersaturated solution of the salt in vitro. The same effect is not observed for IgG antibodies isolated from the joint fluids of patients with other joint diseases, such as pseudogout, rheumatoid arthritis, or osteoarthritis. Furthermore, IgG antibodies obtained from rabbits injected subcutaneously with crystals of MSUM, were also nucleating towards MSUM crystals.

NMR studies of the interaction of chromomycin A3 with small DNA duplexes. Binding to GC-containing sequences

The interaction of chromomycin A3 with the oligodeoxyribonucleotides 1, d(ATGCAT), 2, d(ATCGAT), 3, d(TATGCATA), and 4, d(ATAGCTAT), has been investigated by 1H and 31P NMR. In the presence of Mg2+, chromomycin binds strongly to the three GC-containing oligomers 1, 3, and 4 but not to the CG-containing oligomer 2. The proton chemical shift changes for 1 and 3 are similar, and these DNA duplexes appear to bind with a stoichiometry of 2 drugs:1 Mg2+:1 duplex. The same stoichiometry of 2 drugs:1 duplex is confirmed with 4; however, proton chemical shift changes differ. An overall C2 symmetry is exhibited by the drug complex with 1, 3, and 4. At a molar ratio of 2.0 (drugs:duplex), no free DNA proton NMR signals remain. Two-dimensional nuclear Overhauser exchange spectroscopy (NOESY) of the saturated chromomycin complex with 1 and 3 positions both chromomycinone hydroxyls and the E carbohydrates in the minor groove and provides evidence suggesting that the B carbohydrates lie on the major-groove side. This is supported by several dipolar coupling cross-peaks between the drug and the DNA duplex. Drug-induced conformational changes in duplex 1 are evaluated over a range of NOESY mixing times and found to possess some characteristics of both B-DNA and A-DNA, where the minor groove is wider and shallower. A widening of the minor groove is essential for the DNA duplex to accommodate two drug molecules. This current minor-groove model is a substantial revision of our earlier major-groove model [Keniry, M.A., Brown, S.C., Berman, E., & Shafer, R.H. (1987) Biochemistry 26, 1058-1067] and is in agreement with the model recently proposed by Gao and Patel [Gao, X., & Patel, D. J. (1989a) Biochemistry 28, 751-762].