Characterization of the triterpene saponins of the roots and rhizomes of blue cohosh (Caulophyllum thalictroides)

Seven triterpene saponins were isolated from n-butanol fractions of blue cohosh (Caulophyllum thalictroides) roots and rhizomes. Their structures were established by spectral ((1)H NMR, (13)C NMR, 2D-NMR, and APCI-MS) techniques and chemical reactions as hederagenin 3-O-alpha-L-arabinopyranoside (1); caulophyllogenin 3-O-alpha-L-arabinopyranoside (2); hederagenin 3-O-beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinopyranoside (3); 3-O-alpha-L-arabinopyranosyl-hederagenin 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranoside (4); 3-O-alpha-L-arabinopyranosyl- caulophyllogenin 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranoside (5); 3-O-beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinopyranosyl- echinocystic acid 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranoside (6); 3-O-beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-hederagenin 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl(1-->6)-beta-D-glucopyranoside (7). All seven compounds were identified in this species for the first time.

Structural evaluation of phospholipid bicelles for solution-state studies of membrane-associated biomolecules

Several complementary physical techniques have been used to characterize the aggregate structures formed in solutions containing dimyristoylphosphatidylcholine (DMPC)/dihexanoylphosphatidylcholine (DHPC) at ratios of < or =0.5 and to establish their morphology and lipid organization as that of bicelles. (31)P NMR studies showed that the DMPC and DHPC components were highly segregated over a wide range of DMPC/DHPC ratios (q = 0.05-0.5) and temperatures (15 degrees C and 37 degrees C). Only at phospholipid concentrations below 130 mM did the bicelles appear to undergo a change in morphology. These results were corroborated by fluorescence data, which demonstrated the inverse dependence of bicelle size on phospholipid concentration as well as a distinctive change in phospholipid arrangement at low concentrations. In addition, dynamic light scattering and electron microscopy studies supported the hypothesis that the bicellar phospholipid aggregates are disk-shaped. The radius of the planar domain of the disk was found to be directly proportional to the ratio of DMPC/DHPC and inversely proportional to the total phospholipid concentration when the DMPC/DHPC ratio was held constant at 0.5. Taken together, these results suggest that bicelles with low q retain the morphology and bilayer organization typical of their liquid-crystalline counterparts, making them useful membrane mimetics.

Flavonol glycosides and novel iridoid glycoside from the leaves of Morinda citrifolia

One new iridoid glycoside and five known flavonol glycosides have been isolated from the leaves of Morinda citrifolia. The new iridoid exists as an epimeric mixture in solution. Complete assignments of the proton and carbon chemical shifts for the individual epimers were accomplished on the basis of high-resolution 1D and 2D NMR data. Their antioxidative activities were measured. All of these compounds showed DPPH free radical scavenging activity at the concentration of 30 microM.

NMR studies of molecular structure in fruit cuticle polyesters

The cuticle of higher plants functions primarily as a protective barrier for the leaves and fruits, controlling microbial attack as well as the diffusion of water and chemicals from the outside environment. Its major chemical constituents are waxes (for waterproofing) and cutin (a structural support polymer). However, the insolubility of cutin has hampered investigations of its covalent structure and domain architecture, which are viewed as essential for the design of crop protection strategies and the development of improved synthetic waterproofing materials. Recently developed strategies designed to meet these investigative challenges include partial depolymerization using enzymatic or chemical reagents and spectroscopic examination of the intact polyesters in a solvent-swelled form. The soluble oligomers from degradative treatments of lime fruit cutin are composed primarily of the expected 10,16-dihydroxyhexadecanoic and 16-hydroxy-10-oxo-hexadecanoic acids; low-temperature HF treatments also reveal sugar units that are covalently attached to the hydroxyfatty acids. Parallel investigations of solvent-swollen cutin using 2D NMR spectroscopy assisted by magic-angle spinning yield well-resolved spectra that permit detailed comparisons to be made among chemical moieties present in the intact biopolymer, the soluble degradation products, and the unreacted solid residue.

Iridoid glycosides from the leaves of Morinda citrifolia

A new iridoid glucoside (1), named citrifolinoside A, was isolated from the leaves of Morinda citrifolia along with the known iridoids asperuloside and asperulosidic acid. The structure of 1 was established by interpretation and full assignments of NMR spectroscopic data.

The influence of water on the nanomechanical behavior of the plant biopolyester cutin as studied by AFM and solid-state NMR

Atomic force microscopy and solid-state nuclear magnetic resonance have been used to investigate the effect of water absorption on the nanoscale elastic properties of the biopolyester, cutin, isolated from tomato fruit cuticle. Changes in the humidity and temperature at which fruits are grown or stored can affect the plant surface (cuticle) and modify its susceptibility to pathogenic attack by altering the cuticle's rheological properties. In this work, atomic force microscopy measurements of the surface mechanical properties of isolated plant cutin have been made as a first step to probing the impact of water uptake from the environment on surface flexibility. A dramatic decrease in surface elastic modulus (from approximately 32 to approximately 6 MPa) accompanies increases in water content as small as 2 wt %. Complementary solid-state nuclear magnetic resonance measurements reveal enhanced local mobility of the acyl chain segments with increasing water content, even at molecular sites remote from the covalent cross-links that are likely to play a crucial role in cutin's elastic properties.

Biosynthesis, molecular structure, and domain architecture of potato suberin: a (13)C NMR study using isotopically labeled precursors

Although suberin in potato wound periderm is known to be a polyester containing long-chain fatty acids and phenolics embedded within the cell wall, many aspects of its molecular structure and polymer-polymer connectivities remain elusive. The present work combines biosynthetic incorporation of site-specifically (13)C-enriched acetates and phenylalanines with one- and two-dimensional solid-state (13)C NMR spectroscopic methods to monitor the developing suberin polymer. Exogenous acetate is found to be incorporated preferentially at the carboxyl end of the aliphatic carbon chains, suggesting addition during the later elongation steps of fatty acid synthesis. Carboxyl-labeled phenylalanine precursors provide evidence for the concurrent development of phenolic esters and of monolignols typical of lignin. Experiments with ring-labeled phenylalanine precursors demonstrate a predominance of sinapyl and guaiacyl structures among suberin's phenolic moieties. Finally, the analysis of spin-exchange (solid-state NOESY) NMR experiments in ring-labeled suberin indicates distances of no more than 0.5 nm between pairs of phenolic and oxymethine carbons, which are attributed to the aromatic-aliphatic polyester and the cell wall polysaccharide matrix, respectively. These results offer direct and detailed molecular information regarding the insoluble intermediates of suberin biosynthesis, indicate probable covalent linkages between moieties of its polyester and polysaccharide domains, and yield a clearer overall picture of this agriculturally important protective material.

NMR studies of structure and dynamics in fruit cuticle polyesters

Cutin and suberin are support polymers involved in waterproofing the leaves and fruits of higher plants, regulating the flow of nutrients among various plant organs, and minimizing the deleterious impact of microbial pathogens. Despite the complexity and intractable nature of these plant biopolyesters, their molecular structure and development are amenable to study by suitable solid-state and solution-state NMR techniques. Interactions of tomato cutin with water were examined by solid-state 2H and 13C NMR, showing that water films enhance rapid segmental motions of the acyl chains and are associated with a fivefold increase in surface elasticity upon cutin hydration. The suberization of wounded potato tissues was studied by solid-state 13C NMR, revealing the likely phenylpropanoid structures that permit dense cross-linking of the suberin structure and their proximity to the cell-wall polysaccharides. Finally, two new approaches were developed to elucidate the molecular structures of these biopolymers: partial depolymerization followed by spectroscopic analysis of the soluble oligomers; and swelling of the intact materials followed by magic-angle spinning (MAS) NMR analysis.

Re-analysis of magic angle spinning nuclear magnetic resonance determination of interlamellar waters in lipid bilayer dispersions

A recent method to obtain the number of water molecules of hydration of multilamellar lipid vesicles using magic angle spinning nuclear magnetic resonance has been re-examined. The previous interpretation divided the water into bulk and interlamellar water and ignored water in defects (lakes) that are intrinsic to multilamellar lipid vesicles; the result was inconsistent with x-ray results for the lipid DOPC. The new interpretation takes advantage of the reduction of lake water with increased spinning and it uses osmotic pressure measurements to determine the loss of interlamellar water. The new result for DOPC from magic angle spinning is consistent with x-ray results.

Long-distance rotational echo double resonance measurements for the determination of secondary structure and conformational heterogeneity in peptides

The utility of rotational echo double resonance (REDOR) NMR spectroscopy for determining the conformations of linear peptides has been examined critically using a series of crystalline and amorphous samples. The focus of the present work was the evaluation of long-distance (> 5 A) interactions using 13C-15N dephasing. Detailed studies of specifically labeled melanostatin and synthetic analogs of the alpha-factor yeast mating hormone show that nitrogen-dephased, carbon-observe REDOR measurements are reliable for distances up to 6.0 A, and that dipolar interactions can be detected for distances up to 7 A. By contrast, nitrogen-observe REDOR gives reliable results only for distances shorter than 5.0 A. To measure distances accurately, REDOR data must be corrected for the effects of natural-abundance spins. These corrections are particularly important for measuring long distances, which are of the greatest value for determining peptide secondary structure. We have developed a spherical shell model for calculating the effect of these background spins. The REDOR studies also indicate that in a lyophilized powder, the tridecapeptide alpha-factor mating pheromone from Saccharomyces cerevisiae (WHWLQLKPGQPMY) probably exists as a distribution of different turn structures around the KPGQ region. This finding revises previous solid-state NMR studies on this peptide, which concluded alpha-factor assumes a distorted type-I beta-turn in the Pro-Gly central region of the molecule [J.R. Garbow, M. Breslav, O. Antohi, F. Naider, Biochemistry, 33 (1994) 10094].

Glycerol is a suberin monomer. New experimental evidence for an old hypothesis

The monomer composition of the esterified part of suberin can be determined using gas chromatography-mass spectroscopy technology and is accordingly believed to be well known. However, evidence was presented recently indicating that the suberin of green cotton (Gossypium hirsutum cv Green Lint) fibers contains substantial amounts of esterified glycerol. This observation is confirmed in the present report by a sodium dodecyl sulfate extraction of membrane lipids and by a developmental study, demonstrating the correlated accumulation of glycerol and established suberin monomers. Corresponding amounts of glycerol also occur in the suberin of the periderm of cotton stems and potato (Solanum tuberosum) tubers. A periderm preparation of wound-healing potato tuber storage parenchyma was further purified by different treatments. As the purification proceeded, the concentration of glycerol increased at about the same rate as that of alpha,omega-alkanedioic acids, the most diagnostic suberin monomers. Therefore, it is proposed that glycerol is a monomer of suberins in general and can cross-link aliphatic and aromatic suberin domains, corresponding to the electron-translucent and electron-opaque suberin lamellae, respectively. This proposal is consistent with the reported dimensions of the electron-translucent suberin lamellae.

Complete isomer-specific 1H and 13C NMR assignments of the heme resonances of rat liver outer mitochondrial membrane cytochrome b5

Singly and doubly labeled delta-aminolevulinic acid derivatives were used to prepare rat liver outer mitochondrial membrane (OM) cytochrome b5 containing a 13C-labeled heme active site. A variety of NMR experiments, including HMBC and INADEQUATE in conjunction with the more commonly used HMQC, NOESY, and COSY, were conducted to make unambiguous assignments of protonated carbons and the quaternary pyrrole-alpha and -beta carbons in both isomeric forms of the paramagnetic active center of OM cytochrome b5. Because the long interpulse delays in the HMBC experiment have a detrimental effect on the detectability of fast relaxing paramagnetically affected resonances. INADEQUATE is proposed as the experiment of choice for assigning quaternary carbons in paramagnetic hemes with carefully chosen macrocycle labeling patterns. Furthermore, the applicability of the INADEQUATE experiment to paramagnetic heme active sites should be facilitated greatly by the availability of biosynthetic methods for producing isotopically labeled b-hemes and, more recently, isotopically labeled c-hemes.

Studies of phospholipid hydration by high-resolution magic-angle spinning nuclear magnetic resonance

A sample preparation method using spherical glass ampoules has been used to achieve 1.5-Hz resolution in 1H magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of aqueous multilamellar dispersions of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), serving to differentiate between slowly exchanging interlamellar and bulk water and to reveal new molecular-level information about hydration phenomena in these model biological membranes. The average numbers of interlamellar water molecules in multilamellar vesicles (MLVs) of DOPC and POPC were found to be 37.5 +/- 1 and 37.2 +/- 1, respectively, at a spinning speed of 3 kHz. Even at speeds as high as 9 kHz, the number of interlamellar waters remained as high as 31, arguing against dehydration effects for DOPC and POPC. Both homonuclear and heteronuclear nuclear Overhauser enhancement spectroscopy (NOESY and HOESY) were used to establish the location of water near the headgroup of a PC bilayer. 1H NMR comparisons of DOPC with a lipid that can hydrogen bond (monomethyldioleoylphosphatidylethanolamine, MeDOPE) showed the following trends: 1) the interlamellar water resonance was shifted to lower frequency for DOPC but to higher frequency for MeDOPE, 2) the chemical shift variation with temperature for interlamellar water was less than that of bulk water for MeDOPE MLVs, 3) water exchange between the two lipids was rapid on the NMR time scale if they were mixed in the same bilayer, 4) water exchange was slow if they were present in separate MLVs, and 5) exchange between bulk and interlamellar water was found by two-dimensional exchange experiments to be slow, and the exchange rate should be less than 157 Hz. These results illustrate the utility of ultra-high-resolution 1H MAS NMR for determining the nature and extent of lipid hydration as well as the arrangement of nuclei at the membrane/water interface.

An 1H-13C-13C-edited 1H NMR experiment for making resonance assignments in the active site of heme proteins

In paramagnetic heme proteins, it is often problematic to make proton resonance assignments for heme substituents that do not have large isotropic shifts and consequently lie under the large envelope of polypeptide resonances. Furthermore, assignments that would normally be performed with the aid of HMBC experiments in diamagnetic molecules can prove difficult in the active site of paramagnetic heme proteins if T2(-1) > 2JCH. To circumvent this problem, a new method is presented to selectively detect 1H in 1Hn-13C-13C fragments biosynthetically introduced into the active site of heme proteins. The pulse sequence combines well-known building blocks such as INEPT to transfer 1H spin magnetization to bonded 13C nuclei, followed by INADEQUATE to generate 13C-13C double-quantum coherence that is selected with pulsed field gradients, and finally reverse-INEPT to transfer magnetization back to 1H nuclei for subsequent observation. The new 1Hn-13C-13C edited experiment takes advantage of the relatively large values of 1JCH and 1JCC, avoiding the long interpulse delays in HMBC that compromise the detectability of rapidly relaxing nuclei. The potential applicability of the pulse sequence is demonstrated by its contribution to the unambiguous assignment of the carbonyl carbons in the heme propionates of ferricytochrome b5.

Follow-up study of a right- and a left-hemispherectomized child: implications for localization and impairment of language in children

Two hemispherectomized girls, one operated on the right, the other on the left, were followed from time of surgery until 9 and 10 years of age and compared with respect to course of language acquisition following surgery. At conclusion of follow-up, receptive and expressive language, phoneme perception and production, and sentence processing of the two hemispherectomized children were compared with those of two control groups of similar age, one developing language normally, the other language-impaired. The left-hemispherectomized child's abilities were similar to those of the language-impaired children; the right-hemispherectomized child's abilities resembled those of the language-normal children. Implications for localization of developmental anomalies in language-impaired children are discussed.

13C NMR spectroscopic and X-ray crystallographic study of the role played by mitochondrial cytochrome b5 heme propionates in the electrostatic binding to cytochrome c

The role played by the outer mitochondrial membrane (OM) cytochrome b5 heme propionate groups in the electrostatic binding between OM cytochrome b5 and horse heart cytochrome c was investigated by 13C NMR spectroscopy and X-ray crystallography. To achieve these aims, 13C-labeled heme OM cytochrome b5 was expressed in Escherichia coli as previously described [Rivera M., Walker, F.A. (1995) Anal. Biochem. 230, 295-302]. Assignment of the resonances arising from the heme propionate carbons in ferricytochrome b5 was carried out by a combination of one- and two-dimensional NMR experiments. Titrations of [13C]heme-labeled OM cytochrome b5 with horse heart cytochrome c were carried out in order to monitor the resonances arising from the heme propionate carbonyl carbons in OM cytochrome b5. The results from these titrations clearly show that only the heme propionate located on the exposed heme edge in OM cytochrome b5 participates in the electrostatic stabilization of the complex between OM cytochrome b5 and horse heart cytochrome c. Similar experiments carried out monitoring 13C resonances arising from several other heme substituents demonstrated that the stoichiometry of the complex is 1:1. A conditional binding constant, K which equals 3.8 x 10(4) +/- 1.4 x 10(4) at mu = 0.02 M, was obtained for the formation of the complex by fitting the binding curves obtained experimentally to a model based on this stoichiometry. The X-ray crystal structure of rat liver OM cytochrome b5 solved to 2.7 A resolution shows that the structures of bovine liver microsomal cytochrome b5 and rat liver OM cytochrome b5 are almost identical when compared at medium resolution. The similarity between the two structures, combined with the findings that only the heme propionate located on the exposed heme edge of OM cytochrome b5 participates in the electrostatic binding to cytochrome c and that the stability of this complex is similar to that measured for the association between microsomal cytochrome b5 and cytochrome c, clearly indicates that the site of interaction on OM cytochrome b5 is almost identical to the one elucidated for microsomal cytochrome b5. It is therefore possible to conclude that the large body of information gathered by many investigators for the nonphysiological interaction between microsomal cytochrome b5 and cytochrome c (recently reviewed) [Mauk, A. G. Mauk, M. R., Moore, G. R., & Northrup, S. H. (1995) Bioenerg. Biomembr. 27, 311-330] has indeed biological as well as pedagogical validity.

The affinities of procolipase and colipase for interfaces are regulated by lipids

It has been suggested that at physiological pH, the trypsin-catalyzed activation of the lipase cofactor, procolipase, to colipase has no consequence for intestinal lipolysis and serves primarily to release the N-terminal pentapeptide, enterostatin, a satiety factor (Larsson, A., and C. Erlanson-Albertsson 1991. The effect of pancreatic procolipase and colipase on pancreatic lipase activation. Biochim. Biophys. Acta 1083:283-288). This hypothesis was tested by measuring the adsorption of [14C]colipase to monolayers of 1-stearoyl-2-oleoyl-sn-3-glycerophosphocholine and 13, 16-cis, cis-docosadienoic acid in the presence and absence of procolipase. With saturating [14C]colipase in the subphase, the surface excess of [14C]colipase is 29% higher than that of procolipase, indicating that colipase packs more tightly in the interface. With [14C]colipase-procolipase mixtures, the proteins compete equally for occupancy of the argon-buffer interface. However, if a monolayer of either or both lipids is present, [14C]colipase dominates the adsorption process, even if bile salt is present in the subphase. If [14C]colipase and procolipase are premixed for > 12 h at pH approximately 8, this dominance is partial. If they are not premixed, procolipase is essentially excluded from the interface, even if procolipase is added before [14C]colipase. These results suggest that the tryptic cleavage of the N-terminal pentapeptide of procolipase may be of physiological consequence in the intestine.

Evaluating spin diffusion in MAS-NOESY spectra of phospholipid multibilayers

Biological semisolids such as aqueous phospholipid dispersions are amenable to experiments that combine magic-angle spinning (MAS) to yield high-resolution 1H NMR-spectra and two-dimensional nuclear Overhauser spectroscopy (NOESY) to estimate proton-proton distances. Using several selectively deuterated dimyristoylphosphatidylcholines, a systematic investigation has been made into the origin of an anomalous NOESY crosspeak between methyl groups of the lipid headgroup and the acyl chains. Although the spin-relaxation and line-narrowing behavior in these multilamellar systems argue against efficient spin diffusion, interdigitated or chain-bendback structural models that bring these 1H nuclei into close proximity are not implicated by the MAS-NOESY results for this phospholipid system. A mechanism has been proposed for spin communication between the two types of methyl protons within a conventional lipid bilayer structure: through-space interactions link the headgroup and backbone protons on adjacent molecules, and then spin diffusion occurs along the acyl chains.

Vowel perception in children with and without language impairment

Twenty-four children with language impairment (LI) and 22 children without language impairment (LN) participated in a study of discrimination, identification, and serial ordering of the highly dissimilar vowels/a/ versus /i/, and the highly similar vowels /epsilon/ versus /ae/. The vowel pairs were presented to the subjects in long- and short-duration sets. Both groups had greater difficulty in identifying /epsilon/ versus /ae/ than /a/ versus /i/. Neither group had greater difficulty with the short- than the long-duration vowel sets. The LI children were less efficient than the LN in identifying /a/ versus /i/, but could identify them accurately. They were significantly less accurate than the LN in identifying /epsilon/ versus /ae/. The majority of the children who could identify the /a/ and /i/ vowels were able to order them serially as well, although this second task appeared to be more difficult than identification. Fewer LI than LN children were able to proceed to the serial ordering task with /epsilon/ and /ae/. The children who could not identify the vowels within a set were almost always able to discriminate them. It was concluded that LI children have an auditory perceptual learning deficit and consequently a less robust central representation for steady state vowels than LN.

Perception of stop consonants in children with expressive and receptive-expressive language impairments

The performance of 32 children with language impairment-11 with expressive language impairment only (LI-E subgroup) and 21 with both receptive and expressive language impairment (LI-ER subgroup)-and of 22 children without language impairment (LN subgroup) was examined in a study of perception and imitation of synthesized /ba/ and /da/ syllables. Formant transition duration and task difficulty were varied in the perceptual tasks. The LI-E children were able to identify the syllables as well as the LN; the LI-ER were not. Of the children who succeeded on an identification task and proceeded to a serial ordering task incorporating the same stimuli, the LI-E children were the least successful on the second task. The ability to label the stimuli perceptually was highly correlated with absence of speech articulation errors in the LI children and with performance on the imitation task in all subjects. The findings are examined in relation to the hypotheses that rapid-rate perceptual processing is the sole basis of language impairment in children and that, in these children, production skill may predict phoneme perception rather than the reverse.

Aromatic amino acid transamination and methionine recycling in trypanosomatids

Although trypanosomatids are known to rapidly transaminate exogenous aromatic amino acids in vitro and in vivo, the physiological significance of this reaction is not understood. In postmitochondrial supernatants prepared from Trypanosoma brucei brucei and Crithidia fasciculata, we have found that aromatic amino acids were the preferred amino donors for the transamination of alpha-ketomethiobutyrate to methionine. Intact C. fasciculata grown in the presence of [15N]tyrosine were found to contain detectable [15N]methionine, demonstrating that this reaction occurs in situ in viable cells. This process is the final step in the recycling of methionine from methylthioadenosine, a product of decarboxylated S-adenosylmethionine from the polyamine synthetic pathway. Mammalian liver, in contrast, preferentially used glutamine for this reaction and utilized a narrower range of amino donors than seen with the trypanosomatids. Studies with methylthioadenosine showed that this compound was readily converted to methionine, demonstrating a fully functional methionine-recycling pathway in trypanosomatids.

Nuclear magnetic resonance studies of lipid hydration in monomethyldioleoylphosphatidylethanolamine dispersions

Solid-state proton nuclear magnetic resonance has been used to examine surface hydration in suspensions of monomethyldioleoylphosphatidylethanolamine (MeDOPE). The magic-angle spinning (MAS) 1H spectra for aqueous suspensions of MeDOPE in the L alpha phase exhibited two resonances of roughly equal intensity that could be ascribed to water protons, but both their spin-lattice relaxation times and chemical shifts converged upon conversion to the hexagonal phase. Only a single water peak was observed for analogous samples of dioleoylphosphatidylcholine (DOPC). MAS-assisted two-dimensional nuclear Overhauser effect spectroscopy (NOESY) was conducted for multibilayers of both MeDOPE and DOPC. Through-space interactions were identified between pairs of lipid protons, as expected from their chemical structure. For lamellar suspensions of MeDOPE, positive NOESY cross-peaks were observed between the downfield-shifted water resonance (only) and both CH2N and NH2CH3+ protons of the lipid headgroup. These cross-peaks were not observed in the NOESY spectra of MeDOPE in its hexagonal or cubic phases or for lamellar DOPC reference samples. Taken together, the observation of two water peaks, spin-lattice relaxation behavior, and NOESY connectivities in MeDOPE suspensions support the interpretation that the low-field water peak corresponds to hydrogen-bonded interlamellar water interacting strongly with the lipid. Such a population of water molecules exists in association with MeDOPE in the lamellar phase but not for its inverted phases or for lamellar dispersions of DOPC.

Speech-language outcomes of hemispherectomy in children and young adults

Children and young adults who had undergone right or left hemispherectomy for intractable seizures after a period of normal language acquisition were compared with respect to scores on speech and language tests. The majority of the subjects had full scale IQs in the borderline to mentally retarded range. Language scores were computed in relation to estimated mental age, not chronological age. On this basis, the left hemispherectomized children were more likely to show syntactic comprehension and rapid-rate auditory processing deficits than the right hemispherectomized. The two groups were similar to one another and to normal children in speech production. The findings are discussed in relation to developmental language disorders.

Direct observation of cell wall glucans in whole cells of Saccharomyces cerevisiae by magic-angle spinning 13C-NMR

Intact cells of Saccharomyces cerevisiae were examined as an aqueous paste by 13C-nmr spectroscopy with direct polarization and magic-angle spinning. The spectra obtained were highly resolved, showing numerous resonances in the 60-105 ppm range that were assigned to carbons of a liquid-like domain of the cell wall glucan. Assignments were confirmed by running the spectrum of S. cerevisiae in which the cell wall glucans were labeled with [13C] by feeding the cell [13C]galactose. The spectra indicate that the glucan in the cell wall of intact S. cerevisiae assumes a helical conformation and suggest that strain 17A fed with galactose preferentially incorporates the resulting glucose into beta (1-->3)-linkages.

Following Suberization in Potato Wound Periderm by Histochemical and Solid-State 13C Nuclear Magnetic Resonance Methods

The time course of suberization in wound periderm from potato (Solanum tuberosum L.) has been monitored by histochemical and high-resolution solid-state nuclear magnetic resonance (NMR) methods. Light microscopy conducted after selective staining of the lipid and double-bonded constituents shows that suberin is deposited at the outermost intact cell-wall surface during the first 7 d of wound healing; suberization forms a barrier to tissue infiltration at later times. Cross polarization-magic angle spinning 13C NMR spectra demonstrate the deposition of a polyester containing all major suberin functional groups after just 4 d of wound healing. Initially the suberin includes a large proportion of aromatic groups and fairly short aliphatic chains, but the spectral data demonstrate the growing dominance of long-chain species during the period 7 to 14 d after wounding. The results of preliminary 13C-labeling experiments with sodium [2-13C]acetate and DL-[1-13C]phenylalanine provide an excellent prospectus for future NMR-based studies of suberin biosynthesis.

Multinuclear and magic-angle spinning NMR investigations of molecular organization in phospholipid-triglyceride aqueous dispersions

The supramolecular organization of multi-bilayers formed by aqueous egg phosphatidylcholine-triolein (PC-TO) mixtures has been investigated using 31P, 13C, and 1H nuclear magnetic resonance (NMR). For these emulsions, which mimic substrates in the early hydrolytic stages of fat digestion, the NMR spectra obtained with magic-angle spinning (MAS) exhibit resolution comparable to that of sonicated vesicles and integrated peak intensities consistent with their chemical composition. Both 31P line shapes and MAS sideband patterns from the phosphocholine group indicate that mixing with triolein produces a PC bilayer which remains predominantly liquid crystalline in its organization; nevertheless, anomalous spectral features in MAS spectra may be attributed to additional phases in which the headgroups adopt a different orientation with respect to the bilayer normal, and tight packing enhances phosphorus-phosphorus interactions. 13C and 1H line widths monitored as a function of PC mole fraction, spinning speed, and decoupling strength show that the choline headgroups and glycerol backbones are anchored preferentially in the phospholipid-triglyceride assemblies, whereas all acyl chains become very fluid. The average degree of chain order also decreases for the mixed dispersions, as judged from spinning-sideband intensities in 1H MAS NMR spectra. The absence of proton spin-diffusion effects in the PC-TO multilayers is demonstrated by examination of their spinning sidebands and relaxation times, making it possible to use MAS-assisted two-dimensional NMR to assign overlapped 1H resonances and to identify proximal interactions between the two constituents. The usefulness of these NMR strategies in mechanistic studies of gastric fat digestion is also discussed.

Vocal communication in the first 18 months of life

Fifty-one normally developing infants aged birth to 18 months, 10 or 11 in each of five age groups, were videorecorded in their homes before and after an expected change in the form of their vocalizations and under a set of conditions that reflected common daily occurrences. The vocalizations produced were coded according to their communicative contexts, defined in nonvocal behavioral terms. Communicative codes were assigned to seven major categories. The distribution of codes across categories was found to be different for different age groups. It varied between the first and second observations; however, the pattern of change differed across age groups. Data from individuals were transformed to proportions, to control for individual differences in productivity. They were then found to reflect differences in level of development of vocal communication. It was concluded that vocal communication follows an orderly developmental sequence in normally developing infants in the first 18 months of life.

Quantitation of model digestive mixtures by 13C NMR

13C nuclear magnetic resonance (NMR) spectra were obtained at 50.3 and 100.5 MHz for methanolic and aqueous mixtures of sodium taurocholate, 1-monocapryloyl-rac-glycerol, and caprylic acid. Distortionless Enhancement by Polarization Transfer (DEPT) was used to improve spectral sensitivity and resolution, and to generate calibration curves for quantitative determinations of each lipid in methanol. Alternatively, the heights for nonoverlapping peaks in a 13C NMR spectrum acquired with inverse-gated decoupling provide reliable quantitative estimates for each component of the mixture, particularly when the data are obtained in methanol. These experiments also demonstrate the feasibility of detailed NMR structural investigations in model systems for glyceride digestion.

Magic-angle spinning NMR studies of molecular organization in multibilayers formed by 1-octadecanoyl-2-decanoyl-sn-glycero-3-phosphocholine

Magic-angle spinning 1H and 13C nuclear magnetic resonance (NMR) have been employed to study 50%-by-weight aqueous dispersions of 1-octadecanoyl-2-decanoyl-sn-glycero-3-phosphocholine (C[18]:C[10]PC) and 1-octadecanoyl-2-d19-decanoyl-PC (C[18]:C[10]PC-d19), mixed-chain phospholipids which can form interdigitated multibilayers. The 1H NMR linewidth for methyl protons of the choline headgroup has been used to monitor the liquid crystalline-to-gel (LC-to-G) phase transition and confirm variations between freezing and melting temperatures. Both 1H and 13C spin-lattice relaxation times indicate unusual restrictions on segmental reorientation at megahertz frequencies for C(18):C(10)PC as compared with symmetric-chain species in the LC state; nevertheless each chemical moiety of the mixed-chain phospholipid exhibits motional behavior that may be classified as liquidlike. Two-dimensional nuclear Overhauser spectroscopy (NOESY) on C(18):C(10)PC and C(18):C(10)PC-d19 reveals cross-peaks between the omega-methyl protons of the C18 chain and the N-methyl protons of the phosphocholine headgroup, and several experimental and theoretical considerations argue against an interpretation based on spin diffusion. Using NMR relaxation times and NOESY connectivities along with a computational formalism for four-spin systems (Keepers, J. W., and T. L. James. 1984. J. Magn. Reson. 57:404-426), an estimate of 3.5 A is obtained for the average distance between the omega-methyl protons of the C18 chain and the N-methyl protons of the phosphocholine headgroup. This finding is consistent with a degree of interdigitation similar to that proposed for organized assemblies of gel-state phosphatidylcholine molecules with widely disparate acyl-chain lengths (Hui, S. W., and C.-H. Huang. 1986. Biochemistry. 25:1330-1335); however, acyl-chain bendback or other intermolecular interactions may also contribute to the NOESY results. For multibilayers of C(18):C(10)PC in the gel phase, 13C chemical-shift measurements indicate that trans conformers predominate along both acyl chains. 13C Spin-lattice relaxation times confirm the unusual motional restrictions noted in the LC state; nevertheless, 13C and 1H rotating-frame relaxation times indicate that the interdigitated arrangement enhances chain or bilayer motions which occur at mid-kilohertz frequencies.

Cognitive processing in specifically language-impaired children

Eighteen language-impaired children and 25 non-language-impaired children were evaluated to investigate the relationship between language ability and selected aspects of the five-component problem-solving process defined by Kagan and Kogan (1970). Non-impaired children performed better than language-impaired children on nearly all components of the problem-solving process. Language-impaired children had particular difficulties in the areas of coding and hypothesis generation. In fact, coding ability was inversely related to the number of errors made in hypothesis evaluation. Coding ability was also positively correlated with language ability. The exact causal relationship between coding ability, language ability, and error-making in hypothesis evaluation is unclear; however, improving coding skills through training may increase automaticity and lead to improved performance in the higher levels of the problem-solving process.

C nuclear magnetic resonance study of suberized potato cell wall

High-resolution, solid-state (13)C nuclear magnetic resonance (NMR) spectra are reported for suberized cell wall from potatoes (Solanum tuberosum L.). Through experiments combining the techniques of cross polarization and magic-angle spinning, we verified that suberin, like cutin, is a polyester and demonstrated that it also has phenylpropanoid groups characteristic of lignin. Roughly 50% of the suberized material consists of cell-wall polymers; aromatics and other unsaturated linkages outnumber methylene groups 2:1. In conjunction with traditional direct-polarization NMR results, these experiments provide support for prior suggestions that suberin and cell-wall components are chemically bonded via aromatic groups.

Oral and written language abilities of XXY boys: implications for anticipatory guidance

Previous studies of XXY boys suggest that they are at risk for certain communication disorders involving oral and written language. In this study, the language, reading, and spelling skills of a group of 14 XXY boys identified during neonatal cytogenetic screening were compared with those of a group of 15 control children. The two groups were matched for age, grade, race, parity, birth weight, parental age and education, and socioeconomic status. The mean age of the XXY group was 9 years 7 months and that of the control group was 9 years 3 months. The mean academic grade level for both groups was at the transition between third and fourth grade. There was selective reduction in verbal IQ scores for the XXY group and no significant differences apparent between groups for performance IQ scores. The decrease in verbal IQ was associated with a reduced full-scale IQ and also with significant problems in expressive language, auditory processing abilities, and auditory memory. Word-finding difficulties and problems in the production of syntax were major components of the specific expressive language deficit. Except for difficulties in the understanding of complex sentence structures, the receptive language skills of XXY boys did not differ significantly from those of the control group. These reductions in speech and language abilities correlated with decreased achievement by the XXY group on a variety of reading and spelling tasks. These results suggest that difficulty learning how to read and spell may be due to a preexistent language disability. Early attention to such expressive language problems may be essential to ameliorate secondary maladaptive behaviors due to chronic language-related learning disabilities.

One- and two-dimensional NMR relaxation studies of dynamics and structure in bile salt-phosphatidylcholine mixed micelles

A series of one- and two-dimensional 1H-NMR relaxation measurements has been conducted on simple and mixed micellar aggregates of taurocholate, diphenylvaleroylphosphatidylcholine (diPVPC) and egg yolk phosphatidylcholine (egg PC). The results are interpreted to provide structural and dynamic comparisons between micelles and vesicles, between phospholipids of varying chain length, and between different lipid components within the same micellar aggregate. Both chemical shift changes and two-dimensional nuclear Overhauser effect cross peaks suggest direct interaction of taurocholate and PC chemical sites, although the latter observations may also be accounted for by PC-PC interactions. These experiments demonstrate the promise of NMR relaxation techniques for investigations of molecular organization in model substrate for lipolytic enzymes.

Influence of dilution on the physical state of model bile systems: NMR and quasi-elastic light-scattering investigations

Multinuclear (1H and 31P) nuclear magnetic resonance (NMR) spectroscopy and quasi-elastic light scattering have been used to characterize molecular aggregates formed in dilute sodium taurocholate--egg lecithin solutions. When mixed micelles (1.25 g/dL) are diluted with 150 mM aqueous sodium chloride, light-scattering measurements suggest a transformation from mixed micelles to unilamellar vesicle species. Decreased 1H NMR line widths for bile salt resonances are consistent with predominance of a monomer form. The concurrent appearance of a second phospholipid choline methyl resonance indicates two types of phospholipid environment in slow chemical exchange: this behavior is consistent with small unilamellar vesicles. The appearance of bilayer vesicles in dilute model bile solutions is confirmed by addition of a lanthanide shift reagent (Pr3+), which splits the 1H or 31P head-group peak into two components with distinct chemical shift sensitivities. These mixed micelle and vesicle aggregates are also distinguished by their susceptibility to the lipolytic enzyme phospholipase A2 from cobra venom.

Speech perception development in language-impaired children: a 4-year follow-up study

A group of specifically language-impaired (SLI) children was compared with a matched group of non-SLI children (i.e., children displaying normal language) on tests of speech perception and language ability. The tests were administered longitudinally at times separated by an interval of 4 years. Initially (i.e., Time 1), the groups differed significantly in discrimination, sequencing, and rate processing of and serial memory for synthesized /ba/ and /da/ stimuli. At Time 1, age effects were also observed among both groups of children. That is, performance improved as a function of increased age. At follow-up (i.e., Time 2), performance was at or near ceiling for subjects in both groups, indicating that perceptual development occurred in both groups of children. Results are discussed in relation to the hypothesis that perceptual deficits play a causal role in specific language impairment.

Four-year follow-up study of language impaired children

Children identified as normal or as specifically language impaired (SLI) were given speech, language, and intelligence testing on a longitudinal basis. Fourteen normal and 29 SLI children between the ages of 4 1/2 and 8 years were tested at Time 1. They were retested three to four years later when they were 8 to 12 years old. The results indicated that both the normal and the SLI children continued to develop skills in receptive and expressive language and speech articulation across the 3- to 4-year period intervening between evaluations. Overall, however, the SLI children appeared to develop language skills at a slower than normal rate and 80% of them remained language impaired at Time 2. In addition, the majority of the SLI children manifested reading impairment at Time 2, while none of the normal children did so. The implications for the educational management of SLI children are discussed.

Deuterium nuclear magnetic resonance studies of bile salt/phosphatidylcholine mixed micelles

Mixed micelles of deoxycholate (DOC) and 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) have been prepared in which the POPC was specifically deuterated in the 2-, 6-, 10-, or 16-position of the palmitoyl chain or in the N-methyl position of the choline head group. The deuterium nuclear magnetic resonance (2H NMR) spectrum of each of these specifically deuterated mixed micelles consists of a singlet whose line width depends upon the position of deuteration. Spin-spin relaxation times indicate a gradient of mobility along the POPC palmitoyl chain in the mixed micelle, with a large increase in mobility on going from the 10- to the 16-position. Spin-lattice relaxation times (T1's) demonstrate a similar gradient of mobility. Both trends in NMR relaxation behavior are consistent with a bilayer arrangement for the solubilized POPC. 2H T1 times for DOC/POPC micelles are significantly shorter than those measured in other bilayer systems, indicating unusually tight phospholipid acyl chain packing in the mixed micelle.

Cognitive abilities of language-delayed children

The performance and verbal IQ scores for the WPPSI and WISC-R were compared for two groups of children aged 5 to 8 1/2 years, one normal and one specifically language delayed (SLD). There 34 to 38 children in each group. In accordance with selection procedures, performance IQ scores were not significantly different across the two groups. Both verbal and full scale IQ were significantly lower for the SLD than for the normal group. Profiles of verbal subtest scores differed for normal and SLD children but profiles for performance subtest scores did not. Variability of performance subtest scores was not greater for the SLD than for the normal children. The results do not support the hypothesis that language delay in children is related to a nonverbal cognitive deficit.

Neurological status of language-impaired and normal children

The performance on a neurological test battery of 33 language-impaired children who had no gross neurological findings and 37 normal children controlled for age, performance IQ, and socioeconomic status was compared. The language-impaired group was distinguished by less efficient performance in a number of areas, particularly in tasks involving involving rate of movement, perception of dichhaptic stimuli, and left-right identification. Discriminant function analysis identified six variables that correctly classified 87% of the population into their respective normal and language-impaired groups.

Selection of children with specific language deficits

A standard approach to the selection of children with specific language deficit was devised. The approach was based on a current definition of specific language deficit that depends heavily on exclusion criteria. Children with known language deficit who had hearing impairment, cognitive deficit, neurologic deficit, or emotional or behavioral disorder were excluded. Both the exclusion criteria and the criteria dealing with required extent of language impairment were specified in considerable detail. A total of 132 language-impaired children aged 4-8 1/2 years were assessed. Criteria for selection of a matched group of normal-language children were also specified. The language-impaired children were referred to the project by speech and language clinicians in accordance with a set of broadly defined criteria. Contrary to expectation, less than one third of the children from this group met the more precisely defined criteria employed in the project. In addition, those who were selected did not form a homogeneous group but showed considerable variation in expressive versus receptive language and in articulation skill. The selection approach and its effectiveness for the purposes of clinical research and intervention studies are discussed.

Speech acoustic-cue discrimination abilities of normally developing and language-impaired children

The ability of 35 language impaired (LI) and 38 normally developing children between the ages of 5 and 8 1/2 yr to discriminate between speech stimuli, using an operantly conditioned, nonverbal motor response, was investigated. Six syllable contrasts ([ba] versus [da], [da] versus [ta], [epsilon] versus [ae], [dab] versus [daeb], [sa] versus [sta] and [sa] versus [integral a]) were selected to investigate discrimination of various temporal and spectral cues. Results demonstrated that the LI group made most errors discriminating syllables which were differentiated by consonants and fewest errors on those differentiated by vowels. The normal group made most errors discriminating between syllables including fricatives and brief vowels and fewest errors on stimuli differentiated by stop consonants or vowels in context. The LI group was significantly poorer than the normal in discriminating all syllables that incorporated brief temporal cues followed rapidly in succession by other acoustic cues. They also were impaired in discriminating [sa] versus [integral a]. They were unimpaired discriminating stimuli differentiated by vowels. It is suggested that the particular constraints demonstrated by LI children in their nonverbal and speech processing abilities may be attributed to abnormalities in mechanisms involved in auditory masking.