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Histological staining has long been the gold standard for cancer detection, but it is limited by subjectivity and delayed results. Fourier Transform Infrared Spectroscopy (FTIR) has emerged as a promising technique, offering the advantages of objectivity and real-time analysis. Despite its potential, IR biomarkers developed in different studies are based on varying experimental conditions, including different tissue preparation methods, instrumentation, and patient heterogeneity, which hinder their generalizability and transferability. In this study, tissue spectra from various colorectal cancer cases were systematically collected, and IR biomarkers were developed using the band ratios identified in these spectra. Their ability to differentiate cancer-bearing from non-cancer-bearing tissues was evaluated using a machine learning technique. The results show that the top three biomarkers are b1 (1740/1236), b2 (1740/1162) and b3 (1740/1080). When transferring these biomarkers to a new case (approved under the Ohio State University Institutional Review Board # 2011C0085), b1 effectively differentiates tumor, normal, and margin tissues, while the performance of the b2 and b3 are less satisfactory. This suggests that b1 is more robust and sensitive to key molecular features, whereas b2 and b3 are more likely to be affected by tissue heterogeneity or experimental variations. Combining biomarkers enhances tissue differentiation, but the enhancement plateaus after two to three key biomarkers, as adding more introduces overlapping or redundant information. This study provides a benchmark for future research, with the aim of advancing the clinical translation of noninvasive infrared spectroscopy for intraoperative applications.

We exploit gas-phase cluster ion techniques to provide insight into the local interactions underlying divalent metal ion-driven changes in the spectra of carboxylic acids at the air–water interface. This information clarifies the experimental findings that the CO stretching bands of long-chain acids appear at very similar energies when the head group is deprotonated by high subphase pH or exposed to relatively high concentrations of Ca2+ metal ions. To this end, we report the evolution of the vibrational spectra of size-selected [Ca2+·RCO₂⁻]⁺·(H₂O)n=0 to 12 and RCO₂⁻·(H₂O)n=0 to 14 cluster ions toward the features observed at the air–water interface. Surprisingly, not only does stepwise hydration of the RCO₂⁻ anion and the [Ca2+·RCO₂⁻]⁺ contact ion pair yield solvatochromic responses in opposite directions, but in both cases, the responses of the 2 (symmetric and asymmetric stretching) CO bands to hydration are opposite to each other. The result is that both CO bands evolve toward their interfacial asymptotes from opposite directions. Simulations of the [Ca2+·RCO₂⁻]⁺·(H₂O) n clusters indicate that the metal ion remains directly bound to the head group in a contact ion pair motif as the asymmetric CO stretch converges at the interfacial value by n = 12. This establishes that direct metal complexation or deprotonation can account for the interfacial behavior. We discuss these effects in the context of a model that invokes the water network-dependent local electric field along the C–C bond that connects the head group to the hydrocarbon tail as the key microscopic parameter that is correlated with the observed trends.

Palmitic acid (PA) has been found to be a major constituent in marine aerosols, and is commonly used to investigate organic containing atmospheric aerosols, and is therefore used here as a proxy system. Surface pressure-area isotherms (π-A), Brewster angle microscopy (BAM), and vibrational sum frequency generation (VSFG) were used to observe a PA monolayer during film compression on subphases of ultrapure water, CaCl2 and MgCl2 aqueous solutions, and artificial seawater (ASW). π-A isotherms indicate that salt subphases alter the phase behavior of PA, and BAM further reveals that a condensation of the monolayer occurs when compared to pure water. VSFG spectra and BAM images show that Mg2+ and Ca2+ induce ordering of the PA acyl chains, and it was determined that the interaction of Mg2+ with the monolayer is weaker than Ca2+. π-A isotherms and BAM were also used to monitor mixed monolayers of PA and cerebroside, a simple glycolipid. Results reveal that PA also has a condensing effect on the cerebroside monolayer. Thermodynamic analysis indicates that attractive interactions between the two components exist; this may be due to hydrogen bonding of the galactose and carbonyl headgroups. BAM images of the collapse structures show that mixed monolayers of PA and cerebroside are miscible at all surface pressures. These results suggest that the surface morphology of organic-coated aerosols is influenced by the chemical composition of the aqueous core and the organic film itself.

Sea spray aerosol (SSA) is highly enriched in marine-derived organic compounds during seasons of high biological productivity, and saturated fatty acids comprise one of the most abundant classes of molecules. Fatty acids and other organic compounds form a film on SSA surfaces, and SSA particle surface-area-to-volume ratios are altered during aging in the marine boundary layer (MBL). To understand SSA surface organization and its role during dynamic atmospheric conditions, an SSA proxy fatty acid film and its individual components stearic acid (SA), palmitic acid (PA), and myristic acid (MA) are studied separately using surface pressure–area ( Π − A ) isotherms and Brewster angle microscopy (BAM). The films were spread on an aqueous NaCl subphase at pH 8.2, 5.6, and 2.0 to mimic nascent to aged SSA aqueous core composition in the MBL, respectively. We show that the individual fatty acid behavior differs from that of the SSA proxy film, and at nascent SSA pH the mixture yields a monolayer with intermediate rigidity that folds upon film compression to the collapse state. Acidification causes the SSA proxy film to become more rigid and form 3D nuclei. Our results reveal film morphology alterations, which are related to SSA reflectivity, throughout various stages of SSA aging and provide a better understanding of SSA impacts on climate.

Inorganic salts in marine aerosols play an active role in atmospheric chemistry, particularly in coastal urban regions. The study of the interactions of these ions with water molecules at the aqueous surface helps to elucidate the role of inorganic cations and anions in atmospheric processes. We present surface vibrational sum frequency generation (SFG) spectroscopic and molecular dynamics (MD) studies of aqueous MgCl₂ surfaces as models of marine aerosol. Spectroscopy results reveal that the disturbance of the hydrogen bonding environment of the air/aqueous interface is dependent on the MgCl₂ concentration. At low concentrations (< 1 M) minor changes are observed. At concentrations above 1 M the hydrogen bonding environment is highly perturbed. The 2.1 M intermediate concentration solution shows the largest SFG response relative to the other solutions including concentrations as high as 4.7 M. The enhancement of SFG signal observed for the 2.1 M solution is attributed to a larger SFG-active interfacial region and more strongly oriented water molecules relative to other concentrations. MD simulations reveal concentration dependent compression of stratified layers of ions and water orientation differences at higher concentrations. SFG and MD studies of the dangling OH of the surface water reveal that the topmost water layer is affected structurally at high concentrations (> 3.1 M). Finally, the MgCl₂ concentration effect on a fatty acid coated aqueous surface was investigated and SFG spectra reveal that deprotonation of the carboxylic acid of atmospherically relevant palmitic acid (PA) is accompanied by binding of the Mg²⁺ to the PA headgroup.

We have recently argued that marine interfacial surface tension must have a distinctive biogeography because it is mediated by fresh surfactant macromolecules released locally through the food web. Here we begin the process of quantification for associated climate flux implications. A low dimensionality (planar) equation of state is invoked at the global scale as our main analysis tool. For the reader’s convenience, fundamental surfactant physical chemistry principles are reviewed first, as they pertain to tangential forces that may alter oceanic eddy, ripple, and bubble fields. A model Prandtl (neutral) wind stress regime is defined for demonstration purposes. It is given the usual dependence on roughness, but then in turn on the tension reduction quantity known as surface pressure. This captures the main net influences of biology and detrital organics on global microlayer physics. Based on well-established surrogate species, tangent pressures are related to distributed ecodynamics as reflected by the current marine systems science knowledge base. Reductions to momentum and related heat-vapor exchange plus gas and salt transfer are estimated and placed on a coarse biogeographic grid. High primary production situations appear to strongly control all types of transfer, whether seasonally or regionally. Classic chemical oceanographic data on boundary state composition and behaviors are well reproduced, and there is a high degree of consistency with conventional micrometeorological wisdom. But although our initial best guesses are quite revealing, coordinated laboratory and field experiments will be required to confirm the broad hypotheses even partially. We note that if the concepts have large scale validity, they are super-Gaian. Biological control over key planetary climate-transfer modes may be accomplished through just a single rapidly renewed organic monolayer.

At the air–water interface, interfacial molecular structure, intermolecular interactions, film relaxation and film respreading of model lung surfactant monolayers were studied using vibrational sum frequency generation (VSFG) spectroscopy combined with a Langmuir film balance. Chain-perdeuterated dipalmitoylphosphatidylcholine (DPPC-d62), palmitoyloleoylphosphatidylglycerol (POPG), palmitic acid (PA) and tripalmitin were investigated. In the DPPC-d62–PA binary monolayer, PA showed a condensing effect on the DPPC chains. On the contrary, in the DPPC-d62–POPG binary monolayer, POPG showed a fluidizing effect on the DPPC chains. In the ternary monolayer system of DPPC-d62–POPG–PA, the balance between the fluidizing and the condensing effect was also observed. In addition, the film relaxation behavior of DPPC-d62 and the enhanced film stability of DPPC-d62 caused by the addition of tripalmitin were observed. Real-time VSFG was also employed to study the respreading properties of a complex lung surfactant mixture containing DPPC-d62, POPG, PA and KL4 (a mimic of SP-B) peptide, which revealed DPPC enrichment after film compression.

At the air‐water interface, interfacial molecular structure, intermolecular interactions, film relaxation and film respreading of model lung surfactant monolayers were studied using vibrational sum frequency generation (VSFG) spectroscopy combined with a Langmuir film balance. Chain‐perdeuterated dipalmitoylphosphatidylcholine (DPPC‐d62), palmitoyloleoylphosphatidylglycerol (POPG), palmitic acid (PA) and tripalmitin were investigated. In the DPPC‐d62‐PA binary monolayer, PA showed a condensing effect on the DPPC chains. On the contrary, in the DPPC‐d62‐POPG binary monolayer, POPG showed a fluidizing effect on the DPPC chains. In the ternary monolayer system of DPPC‐d62‐POPG–PA, the balance between the fluidizing and the condensing effect was also observed. In addition, the film relaxation behavior of DPPC‐d62 and the enhanced film stability of DPPC‐d62 caused by the addition of tripalmitin were observed. Real‐time VSFG was also employed to study the respreading properties of a complex lung surfactant mixture containing DPPC‐d62, POPG, PA and KL4 (a mimic of SP‐B) peptide, which revealed DPPC enrichment after film comoression.

Inorganic salts in marine aerosols play an active role in atmospheric chemistry, particularly in coastal urban regions. The study of the interactions of these ions with water molecules at the aqueous surface helps to elucidate the role of inorganic cations and anions in atmospheric processes. We present surface vibrational sum frequency generation (SFG) spectroscopic and molecular dynamics (MD) studies of aqueous ... surfaces as models of marine aerosol. Spectroscopy results reveal that the disturbance of the hydrogen bonding environment of the air/aqueous interface is dependent on the ... concentration. At low concentrations (< 1 M) minor changes are observed. At concentrations above 1 M the hydrogen bonding environment is highly perturbed. The 2.1 M intermediate concentration solution shows the largest SFG response relative to the other solutions including concentrations as high as 4.7 M. The enhancement of SFG signal observed for the 2.1 M solution is attributed to a larger SFG-active interfacial region and more strongly oriented water molecules relative to other concentrations. MD simulations reveal concentration dependent compression of stratified layers of ions and water orientation differences at higher concentrations. SFG and MD studies of the dangling OH of the surface water reveal that the topmost water layer is affected structurally at high concentrations (> 3.1 M). Finally, the ... concentration effect on a fatty acid coated aqueous surface was investigated and SFG spectra reveal that deprotonation of the carboxylic acid of atmospherically relevant palmitic acid (PA) is accompanied by binding of the ... to the PA headgroup. (ProQuest: ... denotes formulae/symbols omitted.)

Inorganic salts in marine aerosols play an active role in atmospheric chemistry, particularly in coastal urban regions. The study of the interactions of these ions with water molecules at the aqueous surface helps to elucidate the role of inorganic cations and anions in atmospheric processes. We present surface vibrational sum frequency generation (SFG) spectroscopic and molecular dynamics (MD) studies of aqueous MgCl 2 surfaces as models of marine aerosol. Spectroscopy results reveal that the disturbance of the hydrogen bonding environment of the air/aqueous interface is dependent on the MgCl 2 concentration. At low concentrations (< 1 M) minor changes are observed. At concentrations above 1 M the hydrogen bonding environment is highly perturbed. The 2.1 M intermediate concentration solution shows the largest SFG response relative to the other solutions including concentrations as high as 4.7 M. The enhancement of SFG signal observed for the 2.1 M solution is attributed to a larger SFG-active interfacial region and more strongly oriented water molecules relative to other concentrations. MD simulations reveal concentration dependent compression of stratified layers of ions and water orientation differences at higher concentrations. SFG and MD studies of the dangling OH of the surface water reveal that the topmost water layer is affected structurally at high concentrations (> 3.1 M). Finally, the MgCl 2 concentration effect on a fatty acid coated aqueous surface was investigated and SFG spectra reveal that deprotonation of the carboxylic acid of atmospherically relevant palmitic acid (PA) is accompanied by binding of the Mg 2+ to the PA headgroup.