Domain: Natural Science — Biochemistry & Molecular Biology
Target concept: Color Change of Glucose Oxidase-Peroxidase in Glucose-Containing Solutions

Video generation prompt: On the bench, two transparent vials were placed side by side; glucose oxidase-peroxidase reagent was added to both, followed by the addition of a glucose solution to the left vial and a glucose-free liquid to the right vial.

Evaluation guide:
Target concept: Substrate-specific enzymatic color generation via coupled GOx-POD-TMB system, where glucose presence triggers irreversible blue-purple chromogen oxidation. Minimum mechanistic assumptions: (i) GOx is active only in presence of glucose and O₂; (ii) POD requires H₂O₂ (product of GOx) to oxidize TMB; (iii) TMB oxidation yields a stable, visible blue-purple product (charge-transfer complex); (iv) absence of glucose → no H₂O₂ → no oxidation → no color. Phased storyline: (1) Baseline: Two identical colorless vials with identical reagent; (2) Intervention: Glucose added to left → enzymatic cascade initiates → H₂O₂ generated → TMB oxidized; (3) Manifestation: Blue-purple color emerges exclusively in left vial within 4 s, with sharp spatial boundary and high chromatic contrast; (4) Control confirmation: Right vial remains indistinguishable from baseline, with no color, no turbidity, no hue shift. Visibility constraints: Must be shot frontally under neutral white light; vials must fill ≥60% of vertical frame; color must be resolvable at 1080p without zoom; no labels required if left/right is unambiguously encoded by consistent spatial position and addition sequence.

Manual:
I. Basic Demonstration Information
Demonstration Title: Glucose Oxidase-Peroxidase Colorimetric Detection of Glucose Demonstration
Subject: Natural Science - Biochemistry & Molecular Biology - Enzyme Kinetics & Assays
Demonstration Purpose: To visually demonstrate the substrate-specific enzymatic color development in glucose detection using the coupled GOx-POD system; to establish visual recognition of the diagnostic color change (colorless → blue/purple) as a direct indicator of glucose presence; and to train discrimination between experimental positive (glucose-containing) and negative (glucose-free) controls.

II. Demonstration Carrier/Equipment
Core Carrier: Two identical 10-mL transparent glass vials (cylindrical, flat-bottomed, clear borosilicate); Glucose oxidase-peroxidase reagent (commercial GOx-POD-TMB mix, amber-brown liquid, ready-to-use); Glucose solution (10 mM in phosphate buffer, colorless, pH 7.0); Glucose-free control liquid (phosphate buffer alone, colorless, identical viscosity and refractive index to glucose solution); Lab bench with neutral matte background; Precision dropper (calibrated, 1 mL graduation).

III. Demonstration Content Description
Layout: Place two vials side-by-side on bench, 3 cm apart, centered in frame. Left vial = test; right vial = control.
State Control: Ensure reagent is homogeneous (no precipitate); solutions at room temperature (22–25°C); no bubbles in vials pre-addition.
Sequence: (1) Add 1.0 mL GOx-POD reagent to each vial (observe meniscus rise); (2) Wait 2 s; (3) Add 0.1 mL glucose solution to left vial; (4) Wait 2 s; (5) Add 0.1 mL glucose-free buffer to right vial.

IV. Observation of Core Phenomena
Expected Phenomenon: Within 3–5 s after step (3), left vial develops a vivid, stable blue-to-purple color (oxidized TMB). Right vial remains completely colorless and transparent before, during, and after step (5).
Visual Verification Features:
- Color Onset: Sudden, localized appearance of blue-purple hue *only* in left vial, beginning at air-liquid interface.
- Hue Specificity: Deep violet-blue (not green, yellow, red, or brown); matches standard TMB oxidation.
- Spatial Exclusivity: No color in right vial at any time — identical optical clarity to baseline.
- Temporal Linkage: Color appears *after* glucose addition, *not* after reagent alone or buffer addition.
- Contrast Stability: Color intensifies then plateaus; contrast ratio (left chromaticity vs. right achromaticity) remains high (>15:1 CIELAB ΔE) throughout observation.

V. Summary of Key Knowledge Points and Principles
Core Concept Definition: The GOx-POD assay is a coupled enzymatic reaction where glucose oxidase (GOx) converts glucose to gluconic acid and H₂O₂, and horseradish peroxidase (POD) uses H₂O₂ to oxidize a chromogenic substrate (e.g., TMB) into a colored product. Color development is strictly dependent on glucose concentration.
Principle of Visual Feature Recognition: Human vision detects the presence of glucose via binary chromatic discrimination — the emergence of a specific, saturated blue-purple hue *only* in the glucose-supplemented vial, against an invariant colorless control. This exploits opponent-color processing (blue-yellow channel activation) for high-contrast, low-threshold detection.

VI. Demonstration Precautions
- Reagent must be fresh (H₂O₂ labile); avoid light exposure pre-use.
- Glucose and buffer must be iso-osmotic and spectrally matched (no UV-absorbing impurities) to prevent false positives/negatives.
- Use identical dropper for both additions to ensure volumetric consistency.
- Record under D65 daylight-equivalent illumination to avoid metamerism (e.g., fluorescent lighting masking purple hue).
- Limit observation to 10 s post-glucose addition — color is stable within this window.

Prompt Grounding rubric:
level_1: No two transparent vials visible; or vials not side-by-side; or no reagent addition shown; or glucose solution added to both/none vials; or glucose-free liquid absent; core spatial layout (left vial = glucose, right vial = glucose-free) completely violated.
level_2: Two transparent vials present and side-by-side, but labeling or spatial assignment ambiguous (e.g., no clear left/right orientation); reagent added to only one vial; or glucose solution added to right vial instead of left; or glucose-free liquid missing/indistinguishable from water; core causal sequence (reagent first → then substrate addition) broken.
level_3: Two transparent vials placed side-by-side with unambiguous left/right positioning; glucose oxidase-peroxidase reagent visibly added to both vials; glucose solution added to left vial and a visibly distinct glucose-free liquid (e.g., distilled water or buffer, colorless and clear) added to right vial; however, reagent addition lacks visual clarity (e.g., no dropper motion, no meniscus change) or timing order is ambiguous (e.g., simultaneous addition without discernible sequence).
level_4: All core spatial and sequential elements correct: vials are identical, transparent, upright, and adjacent; reagent added visibly and sequentially to both vials (e.g., dropper dispenses into each); glucose solution added clearly to left vial (labeled or contextually unambiguous); glucose-free liquid (e.g., distilled water) added to right vial; no misattribution of liquids; minor non-core flaws (e.g., no label text, slight lighting glare obscuring meniscus, no time-lapse acceleration cue).
level_5: Perfect prompt grounding: (i) two identical, cylindrical, transparent glass vials placed precisely side-by-side on a lab bench with neutral background; (ii) identical volume of glucose oxidase-peroxidase reagent (amber/brownish liquid) dispensed via calibrated dropper into each vial, meniscus rise clearly visible; (iii) glucose solution (colorless aqueous) added *only* to left vial with smooth, deliberate motion; (iv) glucose-free liquid (identical in appearance to glucose solution: colorless, clear, same viscosity) added *only* to right vial; (v) left-right assignment is spatially unambiguous (e.g., consistent camera framing, fixed bench reference, or subtle label shadow); all actions occur in strict sequence: reagent → left glucose → right glucose-free.

Scientific and Causal Correctness rubric:
level_1: No color change observed in either vial; or both vials turn same color (e.g., both blue or both purple); or color appears instantly without reagent addition; or color develops before substrate addition; causal chain fully absent or inverted.
level_2: Color change occurs, but violates biochemical logic: e.g., right vial (glucose-free) shows strong color; left vial (glucose) remains colorless; or color is wrong hue (e.g., green/yellow instead of blue/purple); or color appears before reagent addition; no temporal linkage between addition and development.
level_3: Left vial develops visible color (blue or purple) within 2–5 seconds post-glucose addition; right vial remains colorless or shows negligible (sub-threshold) tint; however, color intensity is weak/unstable (fades rapidly), or hue is desaturated (e.g., gray-blue instead of vivid blue); no clear contrast gradient; absence of expected chromogen (e.g., TMB or o-dianisidine analog) implied by incorrect hue.
level_4: Left vial develops a stable, vivid blue-to-purple color (characteristic of oxidized TMB) within 3–6 seconds after glucose addition; right vial remains persistently colorless and transparent throughout; color development is localized to left vial only; hue matches standard peroxidase chromogen oxidation (no yellow/green/red artifacts); causal linkage clear: color appears *only after* glucose addition to left vial, and *not* after glucose-free addition to right.
level_5: Scientifically precise causal fidelity: (i) immediate, localized, and irreversible blue-to-purple color development *exclusively* in left vial within ≤4 seconds of glucose solution addition: hue matches oxidized TMB (λmax ~652 nm, perceptually deep violet-blue); (ii) right vial remains optically identical to pre-addition state: perfectly colorless, transparent, no turbidity or hue shift; (iii) color intensity increases monotonically and saturates within video duration; (iv) no spurious color in reagent-only phase; (v) color change is *caused by* enzymatic cascade: glucose → gluconic acid + H₂O₂ (via GOx) → H₂O₂ + chromogen → oxidized colored product (via POD); this logic is visually embodied by strict substrate-dependence and spatial exclusivity.

Spatiotemporal Consistency rubric:
level_1: Vials appear to float or lack bench contact; inconsistent lighting (e.g., left vial lit, right in shadow); sudden object teleportation or size scaling; frame jumps or flicker disrupting continuity; human hand enters inconsistently (e.g., appears only for left vial); temporal reversal or stuttering.
level_2: Vials anchored on bench but with inconsistent perspective (e.g., left vial frontal, right vial angled); lighting creates false color casts (e.g., blue light makes right vial appear tinted); hand motion jerky or discontinuous; reagent/glucose addition lacks fluid trajectory; time compression causes unnatural acceleration (e.g., instant color without transition).
level_3: Spatial layout stable: vials fixed, parallel, same height, same distance from camera; lighting even and neutral (no hue bias); hand enters frame consistently from bottom center, performs two distinct additions with clear pause between; color develops smoothly over 2–3 seconds in left vial; however, minor inconsistencies: e.g., slight parallax shift between additions, or brief occlusion during right-vial addition, or vial condensation appearing only post-addition.
level_4: High spatiotemporal fidelity: (i) static, orthographic bench view with consistent depth-of-field; (ii) vials maintain identical scale, alignment, and reflection properties; (iii) hand motion is smooth, biomechanically plausible, and spatially registered: approaches left vial, dispenses, withdraws, pauses (~0.5 s), approaches right vial, dispenses; (iv) color development is gradual, uniform, and confined within left vial meniscus; (v) no lighting shifts, no frame drops, no geometry violations; minor imperfection: e.g., one frame of slight motion blur during withdrawal.
level_5: Perfect spatiotemporal coherence: (i) zero camera movement or focus shift; (ii) vials exhibit identical specular highlights, meniscus curvature, and refractive distortion throughout; (iii) hand motion follows natural arc, velocity profile matches human motor control (slight deceleration at target, dwell at dispensing point); (iv) color emergence begins at liquid surface and propagates downward uniformly with laminar diffusion pattern; (v) all transitions (hand entry → reagent addition → glucose addition → color onset → saturation) occur in continuous, physically plausible time progression with no interpolation artifacts; (vi) no perceptual contradictions across frames: every frame self-consistently supports the full causal narrative.