The membrane affinities of the aliphatic amino acid side chains in an alpha-helical context are independent of membrane immersion depth

Understanding, predicting, and designing the binding of peptides and proteins to bilayers require quantifying the intrinsic propensities of individual amino acid residues to bind membranes as a function of structural context and bilayer depth. A host-guest study was performed using the peptide host named helix5 in order to determine the membrane affinities of the aliphatic side chains both in an alpha-helical context and as a function of bilayer depth. Use of the alpha-helical host with a constrained geometry allowed the placement of guest sites at three different depths in bilayers and minimized secondary structural changes due to guest substitutions. Circular dichroism and electron paramagnetic resonance (EPR) were used to characterize the aqueous and bilayer-bound structures of the peptide variants. EPR was also used to measure the bilayer-water partition constants of the peptide variants, and the Delta DeltaGtr values (relative to Gly) of the aliphatic amino acid side chains were subsequently calculated. Surprisingly, the DeltaDeltaGtr values did not significantly vary as a function of the guest site depth in bilayers. In addition, the Delta DeltaGtr values determined in an alpha-helical context are reduced to approximately two-thirds of Delta DeltaGtr values determined in other studies for the bilayer-water and octanol-water partitioning of amino acid side chains in extended and unstructured hosts. Both the relative reduction in Delta DeltaGtr values in the context of an alpha-helical host and the invariance of Delta DeltaGtr values with respect to bilayer depth are consistent with the membrane affinities of the aliphatic residues being largely determined by the classical hydrophobic effect.     

Validation of highly polymorphic fluorescent multiplex short tandem repeat systems using two generations of DNA sequencers

Validation studies are a crucial requirement before implementation of new genetic typing systems for clinical diagnostics or forensic identity. Two different fluorescence-based multiplex DNA profiling systems composed of amelogenin, HumD21S11 and HumFGA (referred to as multiplex 1A), and HumD3S1358, HumD21S11 and HumFGA (multiplex 1B) have been evaluated for use in forensic identification using the Applied Biosystems Model 373A and Prism 377 DNA Sequencers, respectively. Experiments were aimed at defining the limit of target DNA required for reliable profiling, the level of degradation that would still permit amplification of the short tandem repeat (STR) loci examined, and the robustness of each locus in the multiplexes after samples were exposed to environmental insults. In addition, the specificity of the multiplexes was demonstrated using nonhuman DNAs. Forensically relevant samples such as cigarette butts, chewing gum, fingernails and envelope flaps were processed using both an organic extraction procedure and a QIAamp protocol. DNAs and resultant multiplex STR profiles were compared. The validation of the triplex STR systems was extended to include over 140 nonprobative casework specimens and was followed with a close monitoring of initial casework (over 300 exhibits). Our results document the robustness of these multiplex STR profiling systems which, when combined with other multiplex systems, could provide a power of discrimination of approximately 0.9999.     

Specific recognition of HLA-E, but not classical, HLA class I molecules by soluble CD94/NKG2A and NK cells

The CD94/NKG2 receptors expressed by subpopulations of NK cells and T cells have been implicated as receptors for a broad range of both classical and nonclassical HLA class I molecules. To examine the ligand specificity of CD94/NKG2 proteins, a soluble heterodimeric form of the receptor was produced and used in direct binding studies with cells expressing defined HLA class I/peptide complexes. We confirm that CD94/NKG2A specifically interacts with HLA-E and demonstrate that this interaction is dependent on the association of HLA-E with peptide. Moreover, no interaction between CD94/NKG2A and classical HLA class I molecules was observed, as assayed by direct binding of the soluble receptor or by functional assays using CD94/NKG2A+ NK cells. The role of the peptide associated with HLA-E in the interaction between HLA-E and CD94/NKG2A was also assessed. All class I leader sequence peptides tested bound to HLA-E and were recognized by CD94/NKG2A. However, amino acid variations in class I leader sequences affected the stability of HLA-E. Additionally, not all HLA-E/peptide complexes examined were recognized by CD94/NKG2A. Thus CD94/NKG2A recognition of HLA-E is controlled by peptide at two levels; first, peptide must stabilize HLA-E and promote cell surface expression, and second, the HLA-E/peptide complex must form the ligand for CD94/NKG2A.     

A longitudinal study of the relationships between haemostatic, lipid, and oestradiol changes during normal human pregnancy

BACKGROUND: Chronic leukemia is a disease characterized by the malignant proliferation of immunologically incompetent lymphocytes. The knowledge of open heart surgery in patients with this disorder is limited. METHODS: Twelve patients with chronic lymphocytic leukemia underwent open heart surgery (nine coronary artery bypass grafting (CABG), two aortic valve replacement (AVR), one CABG and AVR) from September 1991 to September 1996. There were nine males and three females with a mean age of 68 years (41-81 years). Staging was assigned according to the Rai Classification. There were seven Stage 0, two Stage I, zero Stage II, one Stage III and two Stage IV patients. Cardiopulmonary bypass (CPB) was performed using standard techniques of cannulation, moderate hypothermia and antegrade/retrograde cardioplegia. RESULTS: Hospital mortality occurred in two (17%) patients. Both patients died of sepsis. Hospital morbidity occurred in seven (58%) patients. The most common complications were infections. Five patients were found to have other malignancies (basal cell, laryngeal, prostate, bladder and breast cancers). Transfusion of blood products was required in eight (67%) patients. The average length of stay was 15 days (7-50 days). Follow-up was complete. Late mortality occurred in four patients at a mean of 7 months (1-18 months). All deaths were non-cardiac related (ruptured AAA, kidney failure, respiratory failure and sepsis). Six patients remain alive at a mean of 25 months (1-48 months). CONCLUSION: Hospital mortality and morbidity in patients with chronic lymphocytic leukemia undergoing open heart surgery are high. Infection is the leading cause of hospital death, as well as the most common complication. The majority of patients receive blood products during the course of their hospitalization. Late mortality is high and non-cardiac related. Based on these findings, a re-definition of the aims, goals and expectations of open heart surgery in patients with chronic leukemia is necessary. Suggestions in management are presented.     

小井眼技术的发展与评价

本文报道了用氯化铁水合物催化肉桂酸和异戊醇的酯化作用，探讨了氯化铁催化合成肉桂酸异戊酯的条件。     

Secondary structure mapping of an RNA ligand that has high affinity for the MetJ repressor protein and interference modification analysis of the protein-RNA complex

The secondary structure of an RNA aptamer, which has a high affinity for the Escherichia coli MetJ repressor protein, has been mapped using ribonucleases and with diethyl pyrocarbonate. The RNA ligand is composed of a stem-loop with a highly structured internal loop. Interference modification showed that the bases within the internal loop, and those directly adjacent to it, are important in the binding of the RNA ligand to MetJ. Most of the terminal stem-loop could be removed with little effect on the binding. Ethylation interference suggests that none of the phosphate groups are absolutely essential for tight binding. The data suggest that the MetJ binding site on the aptamer is distinct from that of the natural DNA target, the 8-base pair Met box.     

Airway neural responses to kinins: tachyphylaxis and role of receptor subtypes

Heparitinase cleaves heparan sulfate, a glycosaminoglycan associated with all nucleated mammalian cells and extracellular matrices. Despite the important physiologic role heparitinase is postulated to play in such processes as tumor metastasis and inflammation, the identity of the enzyme remains a matter of controversy and there is a question of whether heparitinase is CTAP III. We report a 900,000-fold purification of heparitinase from human platelets. A multi-step procedure utilizing chromatography on heparin, DEAE, hydroxyapatite and size exclusion matrices was employed and yielded a single protein as judged by Coomassie staining of protein separated by SDS-PAGE. The purified protein had an apparent molecular mass of 35 kDa by size exclusion chromatography and 55 kDa by SDS-PAGE. During purification, heparitinase activity co-eluted from the hydroxyapatite and size exclusion columns with the 35-55 kDa protein, confirming that the purified protein was indeed heparitinase. The 35-55 kDa protein reacted strongly with concanavalin A, a lectin known to bind to heparitinase, further confirming that the protein was heparitinase. Platelet heparitinase formed dimers and tetramers upon storage in a purified form, possibly accounting for the various molecular weights previously reported for the enzyme. A partial amino acid sequence of the protein revealed that heparitinase has not been previously sequenced.     

Kalirin inhibition of inducible nitric-oxide synthase

Nitric oxide (NO) acts as a neurotransmitter. However, excess NO produced from neuronal NO synthase (nNOS) or inducible NOS (iNOS) during inflammation of the central nervous system can be neurotoxic, disrupting neurotransmitter and hormone production and killing neurons. A screen of a hippocampal cDNA library showed that a unique region of the iNOS protein interacts with Kalirin, previously identified as an interactor with a secretory granule peptide biosynthetic enzyme. Kalirin associates with iNOS in vitro and in vivo and inhibits iNOS activity by preventing the formation of iNOS homodimers. Expression of exogenous Kalirin in pituitary cells dramatically reduces iNOS inhibition of ACTH secretion. Thus Kalirin may play a neuroprotective role during inflammation of the central nervous system by inhibiting iNOS activity.